aRE pDF DocumEnts accEssiBLE?  |  RiBERa tuRRó   25

Are PDF Documents Accessible? Mireia Ribera Turró

Adobe PDF is one of the most widely used formats in 
scientific communications and in administrative docu-
ments. In its latest versions it has incorporated structural 
tags and improvements that increase its level of accessi-
bility. This article reviews the concept of accessibility in 
the reading of digital documents and evaluates the acces-
sibility of PDF according to the most widely established 
standards.

In a world in which an increasing amount of informa-tion is circulating in digital format, document acces-sibility is becoming a major concern. Many countries 
have adopted legislative measures concerning digital 
accessibility (see, for example, the Web Accessibility 
Initiative at www.w3.org/WAI/Policy) and the guru of 
the Web, Jakob Nielsen, has included it in several columns 
(Nielsen 1996, 1999) and reports (Coyne and Nielsen 
2001a, 2001b, 2001c; Schade and Neilsen 2002).

Improving document accessibility for disabled per-
sons, including the elderly, offers good business oppor-
tunities for IT firms. For example, Sun has introduced 
strict accessibility guidelines in its Java programming 
language, and Microsoft has incorporated an increasing 
number of assistive technologies in its operating system. 
For its part, Adobe came out clearly in favor of accessibil-
ity in the latest updates of its flagship format, PDF, and its 
free Reader program (Adobe 2005).

The efforts of these and many other companies are 
necessary if persons with disabilities are to be able to 
use products as well as persons without disabilities. In 
an effect similar to that of the cascade of interactions 
that takes place in the search for information in a digital 
library (Bates 2002), the accessibility of a digital product 
is contextual and depends on many layers: the product 
itself, the application used to operate it, the support of 
the operating system, and the additional assistive tech-
nologies used to transform the content (Henry 2007). 
For example, an HTML document is considered to be 
accessible if it complies with the Web Content Accessibility 
Guidelines (WCAG 1.0) (W3C 1999, W3C 2006), but it is 
only usable if the browser with which it is consulted 
provides the options of accessibility (e.g., by allowing 
users to modify the associated style sheet), if the user has 
the necessary assistive technologies—screen magnifiers, 
screen readers, alternate pointing devices, etc.—to use the 
information and functionality contained in the document, 
and if all these tools interact correctly with each other.

This article focuses on the accessibility of the PDF 

due to its importance in the world of digital publishing. 
Though we do not have global statistics on its use, a 
Google search specifying PDF as the format returns 236 
million documents, whereas none of the other recover-
able formats reaches 50 million documents (Postscript 
10 million, Microsoft Word 37 million, Microsoft Excel 
14 million, Microsoft PowerPoint 14 million). (The search 
was performed on April 14, 2007, with the arguments 
filetype:pdf, etc. Values were rounded off to the nearest 
million.) It should be remembered that PDF is the main 
format used for digital publishing of electronic journals 
and for a great variety of administrative documents, 
including e-government communications. Furthermore, 
the subformat PDF/A for archiving is the preferred 
format for digital preservation in many large libraries, 
including the Library of Congress, which recommends it 
for textual documents in which the appearance is more 
relevant than the structure (Library of Congress 2005). 
Finally, according to a study by Forrester Research in 
2005, PDF/A and XML will be the dominant formats in 
document archiving in 2008 (Markham 2005). If our digi-
tal memory is going to be in PDF, we must ensure that it 
is accessible to all persons.

So far, the many studies that have been carried out on 
the accessibility of digital information have considered 
mainly the accessibility of Web content in HTML. Digital 
documents in a broad sense have never been evaluated 
from an accessibility viewpoint, and the only user studies 
carried out on them have dealt with usability—without 
paying particular attention to special capacities (see 
Dillon 2004)—or user preferences with regard to articles 
in electronic format (Tenopir 2003). Because it is a very 
new field, few studies have concentrated on PDF accessi-
bility, and they do not form part of the scientific literature. 
However, Joe Clark and Duff Johnson have published 
some interesting articles on the subject (see Clark 2005, 
Johnson 2006, 2007a, and 2007b). 

n What does accessible really mean?
The most widespread view of digital accessibility is the 
regulatory one. The concept of accessibility of digital 
information was mainly disseminated with the publica-
tion of WCAG 1.0 by the World Wide Web Consortium 
(W3C) as the de facto standard in this area, and with 
its incorporation in the federal legislation of the United 
States. In the United States, compliance with the acces-
sibility guidelines has been used as a requirement in 
calls for tenders, and in some cases bidders have been 
taken to court for failure to comply. From this view-
point, an accessible application is one that is “valid,” i.e., 
approved by the criteria of WCAG 1.0 or Section 508 of 
the Rehabilitation Act (U.S. Access Board) and comply-

mireia Ribera turró (ribera@ub.edu) is professor at Universitat 
de Barcelona Department of Library and Information Science.



26   inFoRmation tEcHnoLoGY anD LiBRaRiEs  |  sEptEmBER 2008

ing with their established checklist (see appendixes for 
the detailed checklist). Products must be certifiable as 
accessible. To facilitate the administrative procedures for 
approving bids, there is great interest in the creation of 
automatic protocols for checking compliance. Examples 
of this are products such as the historic Bobby, the LIFT 
extension for Adobe Dreamweaver, and the new WCAG 
2.0, which is still being revised at the time of submission 
of this manuscript. Some authors have evaluated digital 
journals and database interfaces according to their com-
pliance with these guidelines (e.g., Coonin 2002; Stewart, 
Narendra, and Schmetzke 2005). See the importance of 
the concept “programmatically determined” in the draft 
version of WCAG 2.0 (W3C 2006).

The international standard defined by ISO 16071:2003 
offers a different definition of accessibility. It considers 
accessibility to be “the usability of a product, service, 
environment, or facility by people with the widest range 
of capabilities” (ISO 16071:2003). In other words, acces-
sibility is considered equivalent to usability, with the 
sole difference that the objective users are not specified 
but rather defined broadly as having “the widest range 
of capabilities.” If we consult the standard definition of 
usability (ISO 9241-11:1998), we can rewrite the definition 
of accessibility as “the extent to which a product can be 
used (by users with the widest range of capabilities) to 
achieve specified goals with effectiveness, efficiency, and 
satisfaction in a specified context of use.”

Accessibility must also be measured according to the 
parameters of efficacy, efficiency, and satisfaction for the 
type of user (Hornbaek 2006). Furthermore, one should 
not consider the accessibility of a product in general, but 
rather in a given context and for given tasks. According 
to this definition, it would not be appropriate to state that 
“the website of the company company.com is accessible.” 
We should state that “the website of the company com-
pany.com is accessible for broadband connections in office 
environments with the browsers Internet Explorer 6.0 or 
later and Mozilla Firefox 7 or later, and for commercial 
transactions.” A new concept, the “baseline,” appears is 
WCAG 2.0. It marks a great change in the philosophy of 
website accessibility. The baseline defines the context of 
the software platform, and the accessibility can be evalu-
ated only in this context. Specifying the context is particu-
larly important because some authors have seen a parallel 
between disabled users and disabling situations, which 
arise increasingly with the new paradigm of ubiquitous 
computation (Newell 1995). For example, a person suffer-
ing from deafness may have the same problems of access 
as a user in a noisy environment (a discotheque) or one in 
which silence is compulsory (a hospital or library).

Accessibility is also linked to computer manipulability. 
According to the MVC (Model-View-Controller) pattern, 
the final format or document should allow its content, its 
presentation, and its interactivity to be manipulated inde-

pendently in order to personalize each one according to 
the user’s preferences. For example, a webpage (content) 
should be navigable with a keyboard and with a mouse 
(control), and should be viewable with different font 
sizes, color contrasts, etc. (presentation). The separation 
of presentation and content, for example, through cascad-
ing style sheets (CSS), is thus highly desirable. However, 
there are also other aspects of digital formats related to 
computer manipulability. For example, it is considered 
that an open format is more accessible than a proprietary 
format because it is easier to develop assistive technolo-
gies to take advantage of its potential; a multiplatform 
format is more accessible than a format linked to a par-
ticular platform because it is adapted to a greater diver-
sity of controls; a format that includes characteristics of 
internationalization is more accessible than one that does 
not because it can present a greater wealth of content; and 
a format that uses semantic encoding is more accessible 
than one that uses syntactic encoding because the soft-
ware tools can extract more information from it. 

Finally, several authors in the field of publishing 
(Dechilly 2004) and the field of accessible design (Paciello 
2000, Petrie and Weber 2002) have related the accessibility 
of the digital documents to the structuring of the content 
and its potential transformation. Specifically, Raman 
(1994) defines the accessibility of a digital document as

n  the amount of structural information captured by  
the encoding;

n  the degree to which this structural information is 
available for processing by other applications; and

n  the availability of the appropriate software needed 
to process this structure.

n Disabilities that affect reading and assistive technologies
Returning to the definition of accessibility as being for 
the widest range of capabilities, it is observed that some 
disabilities have direct effects on digital reading and asso-
ciated activities (O’Hara 1996), and that there are some 
well-established assistive technologies that can eliminate 
or minimize these effects.

There are three main groups of print disabilities that 
also affect the comprehension of graphics:

n  All degrees of vision problems, from total blind-
ness to reduced vision, color-blindness, and other 
dysfunctions. The most widely used assistive tech-
nology for total blindness is that of screen read-
ers, which digest the information on the screen 
and transform it into spoken text. Reduced vision 
makes it difficult to read or capture the informa-
tion offered; for persons with this disability, screen 



aRE pDF DocumEnts accEssiBLE?  |  RiBERa tuRRó   27

magnifiers offer an optical zoom of the information 
shown in addition to color and contrast adjust-
ment. In both cases additional information in 
the document is often required, such as explana-
tory subtitles for video recordings and alternative 
descriptions for images.

n  Motor skill problems, particularly those affecting 
the upper extremities. This disability hinders the 
interaction with information and the activation 
of controls, links, and even linear scrolling in 
the document. There are a great variety of assis-
tive technologies for persons with this disability, 
including pointing devices, alternative keyboards, 
voice synthesis technologies for activating controls, 
and even assistive technologies for automatic text 
completion. 

n  Different types of cognitive problems that affect 
reading comprehension. Those caused by dyslexia 
or early deafness can benefit from screen magni-
fiers, screen readers, and automatic text comple-
tion. Those caused by cognitive disabilities—which 
have not been widely studied—often require a 
simplified presentation of the information through 
graphics or very simple language.

n PDF
PDF is the descendent of Postscript and is oriented 
toward presentation. Though recent research has experi-
mented with new, more versatile image models (Bagley, 
Brailsford, and Hardy 2003), these have not yet been 
incorporated in the commercial format, which is still basi-
cally Postscript. PDF is a format of digital dissemination 
that has replicated paper documents for many years. Its 
faithful reproduction and portability on different plat-
forms, in addition to a commercial policy of free dissemi-
nation of the Reader program, have given it a dominant 
market position among digital publishing formats. In 
the latest versions, PDF incorporates functions of digital 
management of access rights (DRM) and allows informa-
tion providers to regulate the permission to view, print, 
extract, and modify the content.

The orientation toward presentation, which has 
turned PDF into the de facto standard in the publishing 
industry, is its main drawback for accessibility. In order 
to solve this, from version 1.4 onward Adobe has incor-
porated structural elements in the format (e.g., structural 
tags). This article therefore only studies the most recent 
versions of the format.

Despite the potential of the format, it is possible to 
create PDF documents of very different qualities. The 
application from which a PDF document is generated 
and the process followed in creating it directly affect 

the accessibility of the resulting document. Specifically,  
PDF can have four increasing levels of accessibility: 

 1. PDF image—no accessibility
 2. PDF text
 3. PDF text, with order
 4. Tagged PDF—maximum accessibility

pDF image documents

A PDF image document is a document obtained from 
scanning or photographing a printed document. Its con-
tent is exclusively the bitmap resulting from the optical 
process. It does not allow searches in the document or text 
extraction because the text is only coded as a graphic.

A PDF image document is similar to a paper docu-
ment in its level of accessibility. For blind persons or 
persons with reading problems (caused by dyslexia or 
early deafness) it must be transformed through an optical 
character recognition process in order to encode the text 
and adapt it to screen readers or alter the presentation. 
The only advantage that the digital presentation may 
have over a paper presentation is the possibility of optical 
zooming and increasing the text size to benefit persons 
with certain visual impairments.

pDF text documents

The second level of accessibility is that of PDF text docu-
ments, which come from the same source as image files 
but have gone through an optical character recognition 
process and incorporate the resulting text in the file. In 
this case it is possible to search the content, export the 
content to a word processor, listen to it with screen read-
ers, and perform other types of conversion. Specifically, 
as of version 6 or later, Reader incorporates the possibility 
of removing columns, viewing the text in negative (white 
on black), increasing the font size, and even hearing it 
with a screen reader.

According to the quality of the OCR used and of the 
subsequent manual revision, these files often contain 
slight typographic errors that may affect the results of 
text searches and also make continued reading more dif-
ficult (especially when a screen reader is being used). If 
the quality of the original is poor, or it is in bad condition, 
OCR programs often make small mistakes. Furthermore, 
if the original has a creative layout in which the order of 
presentation does not correspond to the order of reading, 
the resulting text appears disordered and is therefore 
illegible; this problem can arise due to such common 
structures as footnotes, headers, and margin notes.

pDF documents with ordered text

The third level of accessibility is that of PDF text docu-



28   inFoRmation tEcHnoLoGY anD LiBRaRiEs  |  sEptEmBER 2008

ments in which the correct reading order has been estab-
lished. This can be done when the document is created or 
by editing it at a later stage.

tagged pDF documents

The fourth and highest level of accessibility is when the 
PDF document contains ordered text and structural tags 
to define headers, tables, lists, etc. With this encoding, an 
assistive technology can present a summary of the docu-
ment, facilitate navigation, provide structural informa-
tion of the content, etc.

This fourth level is normally achieved only by post-
processing a PDF document that has already been created. 
When documents are converted from the most widely used 
word processors to PDF, there still arise errors that must be 
revised manually. For example, when tables are converted 
from Microsoft Word to PDF, the tags are created correctly 
in general, but the headers of the tables are not marked 
up because Word does not allow them to be differentiated 
structurally. Another example is the conversion from Open 
Office 2.0, in which the documents created have major  
structural deficiencies.

n Are PDF documents accessible?
Even at the highest level of accessibility, tagged PDF 
document, the aspects discussed above in the definition 
of accessibility must be checked. Though PDF is totally 
multimedia, particularly in the latest versions, and it now 
allows programming to be included, the commonest PDF 
documents are plain documents in which text and images 
are reproduced and the interactivity is reduced to the use 
of forms; these documents will thus be the ones analyzed 
here in an initial approach to PDF accessibility. Though 
this may represent a limitation, in fact it includes most 
of the PDF documents used for electronic journals and 
administrative documents. 

PDF’s accessibility is analyzed from the viewpoint of 
the end users, the readers of the document, so comments 
on the most widespread user agent, Reader, are also 
included. PDF’s compliance with WCAG 1.0, the WCAG 
2.0 draft, and Section 508 is evaluated, and its accessibil-
ity is considered from the viewpoint of the platforms 
on which it runs and the programs that can be used to 
create documents. However, Reader and Adobe Acrobat 
Professional are not evaluated as authoring tools or user 
agents because that is not the focus of this article.

WCAG 1.0

In 1997 the W3C officially created an initiative to foster 
the accessibility of the Web (Engelen 2001), following the 

vision of its creator, Tim Berners Lee: “The power of the 
Web is in its universality. Access by everyone regardless 
of disability is an essential aspect.” The Web Accessibility 
Initiative (WAI, www.w3.org/WAI) works with organiza-
tions around the world to develop strategies, guidelines, 
and resources to help make the Web accessible to people 
with disabilities. W3C-WAI has established three recom-
mendations to improve the accessibility of the Web: 

n  WCAG 1.0, released in May 1999, based on the 
Trace Unified Web Guidelines (version 8), affecting 
Web content in itself (e.g., an HTML page)

n  The Authoring Tool Accessibility Guidelines, 
affecting software used to build websites (e.g., 
Dreamweaver)

n  The User Agents Accessibility Guidelines (UAAG), 
affecting browsers and multimedia players that 
interact with Web content (e.g., Mozilla Firefox)

Of these guidelines, the ones that have had the great-
est impact are WCAG 1.0, because they affect content pro-
viders, such as governments. Most legislations promoting 
digital accessibility have made direct or indirect reference 
to these guidelines.

WCAG 1.0 is divided into in fourteen guidelines or 
general principles of accessible design, which are speci-
fied through several checkpoints. Each checkpoint has a 
priority level based on its impact on accessibility. 

Checkpoints of [Priority 1] are a basic requirement for 
some groups to be able to use Web documents. The 
ones of [Priority 2] will remove significant barriers to 
accessing Web documents. Checkpoints of [Priority 3] 
will improve access to Web documents (W3C 1999). 

WCAG 1.0 is designed to evaluate documents, not 
formats, so in this article the evaluation often refers to 
the potential of the format if it is used properly to create 
documents.

PDF can potentially comply with all the checkpoints 
of WCAG 1.0 applicable to text, images, and forms (its 
multimedia potential has not been analyzed in this arti-
cle) in any priority except for three points:

5.2  Headers for tables of complex data, in Priority 1. 
The current version of PDF only foresees the use 
of TH as the header of tables, specifies attributes 
that allows it to be related to columns or files, but 
provides no mechanism for grouping cells (like 
COLGROUP or ROWGROUP of HTML).

3.4  Relative units in markup language attribute val-
ues and style sheet property values, in Priority 2. 
Though the most recent versions of PDF use CSS, 
the format only allows absolute values to be speci-
fied. However, this does not prevent Reader from 
making extensive zooms of the content of the PDF 



aRE pDF DocumEnts accEssiBLE?  |  RiBERa tuRRó   29

documents.
9.5  Provide keyboard shortcuts, in Priority 3. No 

mechanism is specified for linking a keyboard 
shortcut to a content.

In both Point 4.1, for identifying changes of language, 
and Point 5.1, on simple table headers (both of them in 
Priority 1), although PDF provides for the incorpora-
tion of this information, some experiments carried out 
with the Acrobat Professional tools for conversion from 
Microsoft Word have shown that this information is not 
correctly transferred from the word processor to the PDF 
document. 

For a more detailed analysis, see the tables in appen-
dix A. Here we have only commented on the most  
outstanding aspects.

WCAG 2.0 draft

In the course of time WCAG 1.0 has become out of date. 
The Web of 2007 is very different from that of 1999: The 
increased use of multimedia formats; the growth of Web-
based software, AJAX, the XML subformats; and the 
paradigm of ubiquitous computing have made it neces-
sary to redefine WCAG 1.0 guidelines, which were ini-
tially highly focused on HTML, in order to extend them 
to all types of format; it has been considered necessary 
to be able to define an available software platform base-
line (for a detailed discussion of the differences between 
WCAG 1.0 and WCAG 2.0, see www.webaim.org/stan 
dards/wai/wcag2.php#differences). However, due to 
the enormous success of WCAG 1.0, the development of 
the WCAG 2.0 has been subject to enormous pressure, 
and it has received more comments and suggestions than 
any other guideline of W3C. This is why the process of 
approval is slower than normal, and though publication 
dates have been repeatedly announced, the current docu-
ment is no more than a draft.

WCAG 2.0 has four principles, each one addressed 
by several guidelines. Under each guideline there are 
success criteria used to evaluate conformance to this 
standard for that guideline, which fall into three levels of 
conformance, each representing a higher level of acces-
sibility (W3C 2006).

PDF complies almost absolutely with all the success 
criteria of all the levels of the four principles of accessibil-
ity described in WCAG 2.0.

Only in Principle 3 (which establishes that both the con-
tent and the controls must be understandable), Guideline 
3.1, Level 3, “Make text content readable and understand-
able” does WCAG 2.0 fail in several success criteria:

3.1.3 Offer definitions for words used in an unusual 
way.
3.1.6 Offer the pronunciation of words where meaning 
cannot be determined without pronunciation.

In all of these points, the generic title attribute could 
be used for all the tags, but there is no standard mecha-
nism for differentiating pronunciation or slang.

For a more detailed analysis, see the tables in appen-
dix B. Here we have only commented on the most out-
standing aspects.

section 508 of the Rehabilitation act 

In August 2000 the U.S. Access Board (www.access-board 
.gov), an independent federal group that oversees the 
production of guidelines on accessibility for compliance 
with various legislative measures, published a revised 
amendment of the Rehabilitation Act of 1973, stating that 
the information provided by federal agencies must be 
accessible to people with disabilities (Engelen 2001). As 
Johnson mentions, “The regulations also apply to con-
tractors that submit electronic documents to the federal 
government”(2007b).

Compliance with Section 508 is parallel to compliance 
with WCAG 1.0. PDF complies with all the points except 
the ability to associate data cells and header cells for tables 
that have more than one logical level (checkpoint h).

For a detailed analysis see the tables in appen-
dix C. Here we have only commented on the most  
outstanding aspects.

n Are PDF documents accessible from a computer’s viewpoint?
Some doubt still remains about whether PDF is an open 
or closed format. It is a proprietary format, so strictly 
speaking it is not open, but Adobe systematically pub-
lishes the specification of format and allows it to be used 
by third parties free of charge, simply reserving the intel-
lectual property rights (see Adobe 2006, 32, for the exact 
terms of the Adobe license). Furthermore, Adobe recently 
initiated the process for PDF to become an ISO standard 
(Adobe 2007).

The latest versions of PDF allow content and presen-
tation to be differentiated. The content consists of the 
text and images, and the presentation can be encoded 
like webpages with some properties of CSS version 1 
and 2. The control of the document depends on the pro-
gram used to read it, since PDF does not allow keyboard 
shortcuts or alternative actions to be defined for any 
application. One of its main advantages is that it can be 
reproduced faithfully on any platform, but in terms of 
accessibility it is not multiplatform. The structure, links, 
and forms of Adobe Reader for assistive technologies are 
accessed through the Microsoft Active Accessibility tech-
nology, so they can only be used on Microsoft platforms. 
The screen reader incorporated as of Reader 6 does work 
on both Windows and Macintosh.



30   inFoRmation tEcHnoLoGY anD LiBRaRiEs  |  sEptEmBER 2008

With regard to internationalization, PDF supports 
the UniCode character set and also allows the language 
of the document to be specified on a global and local 
level. Though the specification of the format establishes 
that it supports inverse reading order (e.g., for Arabic 
languages) or vertical reading order (e.g., for Asian lan-
guages), WebAIM (WebAIM 2006) states that it causes 
problems with them.

The structure in a PDF document is transmitted 
mainly through the tags incorporated in the format 
since version 1.4. The standard set of tags is fairly 
limited—more so than that of HTML 4 (see Adobe 
2006, Sections 10.7 and 10.8, for a complete list). The 
set of tags can be extended but always with an equiva-
lent with the standard set, which is the only one sup-
ported by Adobe. The structure is transmitted through 
the Microsoft Active Accessibility (MSAA) technol-
ogy to any assistive technology, so other applications 
can also read it. MSAA provides agents and synthe-
sizers in several languages that do not tend to be 
installed by default but can be downloaded free of 
charge from the Microsoft website (www.microsoft 
.com/msagent/downloads/user.asp). There are cur-
rently few programs that can process this structure, of 
which Reader is the most widespread. Among the screen 
readers, Jaws by FreedomScientific and Windows Eyes 
by GW Micro can also process PDF files on a structural 
level. According to Joe Clark (2005), IBM Home Page 
Reader and Hal Screen Reader by Dolphin can also do 
so. Most of these programs incorporate support for PDF 
in their latest versions, which are not always the most 
widely used.

n Are PDF documents accessible according to the ISO standard?
On this topic, few studies have been made and much 
work remains to be done. Accessibility should be evalu-
ated for the different types of disabilities that affect elec-
tronic reading and for different scenarios and contexts of 
use. Though the tests of users with disabilities are begin-
ning to be generalized, and there are even guidelines 
on how to do them (Coyne and Nielsen 2001a), after an 
extensive bibliographic search I was unable to locate any 
studies evaluating this aspect in PDF.

n  The opinion of the experts
Joe Clark, the author of one of the most important books 
on website accessibility, Building Accessible Websites 
(2003), currently forms part of Adobe’s work group 
on usability and accessibility. He is one of the great-

est proponents of PDF, and claims that it offers some 
advantages of accessibility/usability compared with 
HTML (its greatest competitor for digital documents), 
such as its ability to use footnotes, notes, and comments. 
He gives little importance to the fact that it is a propri-
etary format and argues that the important point is that 
the specification is public. In his article on the acces-
sibility of PDFs (Clark 2005), he defends the use of the 
format compared with others for certain objectives and 
needs: for interactive forms, for documents in revision, 
for design fonts not available in HTML, as a format of 
preservation, and for documents that require the man-
agement of digital rights. With regard to software, he 
makes a great defense of Reader for taking advantage 
of documents and resolving problems of accessibility, 
but recognizes that in the field of authoring tools more 
programs are necessary.

WebAIM, an initiative for accessibility at Utah State 
University, gives its opinion on some points that facilitate 
or hinder the accessibility of PDFs:

n  The screen-reading function only exists in the 
complete version of Reader, and by no means 
offers the same functionality as Jaws or Windows 
Eyes. Furthermore, to use it one must memo-
rize new access keys that are not common to  
other programs.

n The reflowing function is very useful for persons 
who require magnification or who work with small 
screens because it eliminates the horizontal scroll.

n WebAIM recommends the use of HTML for tables, 
particularly if they are complex, because current 
screen readers can process them far better than if 
they are in PDF.

n  WebAIM criticizes the fact that the options for con-
figuring accessibility in Reader are highly oriented 
toward screen readers and magnifiers, and that 
they are only partial and confusing. For example, 
it mentions the fact that it is possible to configure 
some multimedia options but not from the acces-
sibility setup wizard. (WebAIM 2006)

Another aspect that receives constant criticism is 
the cost of creating accessible PDF documents. Though 
throughout this article the accessibility of PDF has been 
studied from the viewpoint of the user, the lack of tools 
for creating documents must also be stressed. Though the 
specification is in theory public and there exist software 
tools (e.g., the PDFLib software library and the XSLT 
transformations in Open Office) to generate tags in a 
PDF that are the result of a document conversion, users 
normally depend on the tools of Microsoft Office and the 
Acrobat Professional program to create accessible PDF 
documents. Even with these tools, editing is not as intui-
tive as editing a plain text tagged with HTML, and it is 



aRE pDF DocumEnts accEssiBLE?  |  RiBERa tuRRó   31

far less maintainable because in PDF tags and content are 
encoded separately.

n Conclusions
As has been seen in the analysis, PDF can be considered 
fairly accessible from many points of view, and its degree 
of compliance with the most widely recognized guide-
lines is fairly high. However, a surprising lack of atten-
tion is paid to complex data tables, which form a very 
important part of scientific articles, one of the main types 
of document encoded in this format. The accessibility of 
PDF has greatly reduced its multiplatform nature and it 
is to be expected that Adobe will gradually resolve this 
point, particularly in the Linux environment that has been 
adopted by many public administrations. An accessible 
and multiplatform PDF is a requisite for a really public  
electronic government. 

The format still faces three major challenges with 
regard to accessibility:

n  The creation of powerful authoring tools that allow 
documents to be edited easily, to be modified, and 
to be partially changed without having to restart 
the cycle of creation. There is a lack of authoring 
tools for creating accessible PDF documents easily 
and a lack of integration of the creation process 
in the most widely used word processors. It is to 
be expected that with the merger of Macromedia 
and Adobe these tools will shortly appear on  
the market.

n A greater opening of the format by Adobe in order 
to foster its extensibility (Adobe recently applied 
for PDF to become an ISA standard), which in digi-
tal articles is beginning to be a requirement for the 
annotation of mathematical or chemical formulas. 
(See, for example, the specific development of the 
Infty project for reading mathematical formulas in 
PDF [Kanahori 2006].)

n  A greater wealth of tags and attributes in order 
to express variants, and additional or comple-
mentary information, such as definitions  
and pronunciation. 

Despite its shortcomings, the possibilities of the PDF 
with regard to accessibility have increased greatly in 
the latest versions, and it is now almost on a level with 
HTML. The existence of Reader with several options for 
facilitating accessible reading increases its attractiveness 
even further. The experts recognize the giant steps made 
by the format, though they are aware of its limitations; for 
the moment their advice is to use the right format for the 
right task. Finally, further research is required in order to 

gather the opinion of users on its accessibility.

Works Cited

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Adobe Acrobat 7.0: A guide for publishing PDF doc-
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ue.pdf (accessed Apr. 17, 2007).

———. 2006. PDF reference: Adobe portable document for-
mat version 1.7, 6th ed. www.adobe.com/devnet/acrobat/
pdfs/pdf_reference.pdf (accessed Apr. 17, 2007).

———. 2007. Adobe to release PDF for industry standardiza-
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pressroom/pressreleases/200701/012907OpenPDFAIIM 
.html (accessed Apr. 17, 2007).

Bagley, S. R., D. F. Brailsford, and M. R. B. Hardy. 2003. Document 
formatting: Creating reusable well-structured PDF as a 
sequence of component object graphic (COG) elements. 
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Bates, M. J. 2002. The cascade of interactions in the digital library 
interface. Information Processing and Management 38, no. 3: 
381–400. 

Clark, J. 2003. Building Accessible Websites. Indianapolis: New 
Riders. 

———. 2005. Facts and opinions about PDF accessibility.  
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pdf_accessibility (accessed Apr. 17, 2007).

Coonin, B. 2002. Establishing accessibility for e-journals:  
A suggested approach. Library Hi Tech 20, no. 2: 207–20. 

Coyne, K. P., and J. Nielsen. 2001a. How to Conduct Usability 
Evaluations for Accessibility: Methodology Guidelines for 
Testing Websites and Intranets with Users Who Use Assistive 
Technology. Fremont, Calif.: Norman Nielsen Group. 

———. 2001b. Beyond ALT text: Making the Web easy to use for 
users with disabilities. Fremont, Calif.: Norman Nielsen 
Group. 

———. 2001c. Web Usability for Senior Citizens: Design Guidelines 
Based On Usability Studies with People Age 65 and Older. 
Fremont, Calif.: Norman Nielsen Group. 

Dechilly, T. 2004. Diffusion de contenus et de documents sur 
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Dillon, A. 2004. Designing Usable Electronic Text. 2nd ed. Boca 
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Engelen, J. 2001. Guidelines for web accessibil-
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Collette and Julio Abascal. London: Taylor  
and Francis.

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design. www.uiaccess.com/accessucd (accessed Apr. 17, 
2007).

Hornbaek, K. 2006. Current practice in measuring usability: 
Challenges to usability studies and research. International 
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ISO 16071:2003. Ergonomics of human-system interaction—
guidance on accessibility from human-computer interfaces. 
Iternational Organization for Standardization, 2003. 

ISO 9241-11:1998. Ergonomic requirements for office work with 
visual display terminals (VDTs)—Part 11: Guidance on 
usability. International Organization for Standardization, 
1998.

Johnson, D. 2006. What are PDF tags and why should I care? 
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tags.php (accessed Apr. 17, 2007).

———. 2007a. PDF goes to ISO: the road ahead. www.planet 
pdf.com/enterprise/article.asp?ContentID=PDF_goes_to_
ISO_-_The_road_ahead&page=0 (accessed Apr. 17, 2007).

———. 2007b. PDF in government. www.acrobatusers.com/
articles/2007/02/pdf_in_government/index.php (accessed 
Apr. 17, 2007).

Kanahori, T. 2006. Scientific PDF document reader with sim-
ple interface for visually impaired people. Conference on 
Computers Helping People with Special Needs (ICCHP 10th), 
University of Linz, Austria. 

Library of Congress. 2005. PDF/X, PDF for prepress graphics 
file exchange. Sustainability of Digital Formats Planning for 
Library of Congress Collections. http://digitalpreservation 
.gov/formats/fdd/fdd000124.shtml (accessed Apr. 17, 
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Markham, R. 2005.  The market for accessible technology—
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use. www.microsoft.com/enable/research/phase1.aspx 
(accessed Apr. 17, 2007). 

Nielsen, Jakob. 1996. Accessible design for users with dis-
abilities. Alertbox: Current Issues in Web Usability, Oct. www 
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———. 1999. Disabled accessibility: The pragmatic approach. 
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for Users with Disabilities. Ed. A. D. N. Edwards, 3–18. 
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O’Hara, K. 1996. Toward a Typology of Reading Goals. No. 
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17, 2007).

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Disabilities. Lawrence, Kans.: CMP Books.

Petrie, Helen and G. Weber. 2002. Reading multimedia docu-
ments. Computers Helping People with Special Needs 8th 
International Conference, ICCHP 2002. Proceedings, 15–20 
July.

Raman, T. V. 1994. Audio system for technical reading. PhD 
Thesis, Cornell University.

Schade, A. and J. Nielsen. 2002. Accessibility and usability of Flash 
for users with disabilities based on best practices for design 
of Flash-based user interfaces, based on usability studies with 
people who use assistive technology. Fremont, Calif.: Norman 
Nielsen Group. 

Stewart, R., V. Narendra, and A. Schmetzke. 2005. Accessibility 
and usability of online library databases. Library Hi Tech 23, 
no. 2: 265–286.

Tenopir, C. 2003. Use and Users of Electronic Library Resources: 
An Overview and Analysis of Recent Research Studies. 
Washington, D.C.: Council on Library and Information 
Resources. http://clir.org/pubs/reports/pub120/pub120.
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U.S. Access Board. 1998. Section 508 of the Rehabilitation Act. U.S. 
Code 29, §794d.

WebAIM. 2006. Accessibility features in Acrobat Reader 7. www 
.webaim.org/resources/reader/index.php (accessed Apr. 
17, 2007).

W3C. 1999. Web Content Accessibility Guidelines 1.0. www 
.w3.org/TR/WAI-WEBCONTENT (accessed Apr. 17, 2007).

W3C. 2006. Web Content Accessibility Guidelines 2.0. W3C working 
draft, Apr. 27, 2006. www.w3.org/TR/WCAG20 (accessed 
Apr. 17, 2007).



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APPENDIx A. WCAG 1.0 checklist of checkpoints

Priority 1 checkpoints

In General (Priority 1) Yes No N/A

1.1 Provide a text equivalent for every non-text element (e.g., via “alt,” “longdesc,” or in element 
content). This includes: images, graphical representations of text (including symbols), image map 
regions, animations (e.g., animated GIFs), applets and programmatic objects, ASCII art, frames, 
scripts, images used as list bullets, spacers, graphical buttons, sounds (played with or without user 
interaction), stand-alone audio files, audio tracks of video, and video. 

x     

2.1 Ensure that all information conveyed with color is also available without color, for example from 
context or markup. 

x     

4.1 Clearly identify changes in the natural language of a document’s text and any text equivalents  
(e.g., captions). 

 x1     

6.1 Organize documents so they may be read without style sheets. For example, when an HTML 
document is rendered without associated style sheets, it must still be possible to read the document. 

x     

6.2 Ensure that equivalents for dynamic content are updated when the dynamic content changes.     x

7.1 Until user agents allow users to control flickering, avoid causing the screen to flicker.     x

14.1 Use the clearest and simplest language appropriate for a site’s content. x     

And if you use images and image maps (Priority 1) Yes No N/A

1.2 Provide redundant text links for each active region of a server-side image map.     x  

9.1 Provide client-side image maps instead of server-side image maps except where the regions 
cannot be defined with an available geometric shape. 

    x

And if you use tables (Priority 1) Yes No N/A

5.1 For data tables, identify row and column headers. x     

5.2 For data tables that have two or more logical levels of row or column headers, use markup to 
associate data cells and header cells. 

  x    

And if you use frames (Priority 1) Yes No N/A

12.1 Title each frame to facilitate frame identification and navigation.     x 

And if you use applets and scripts (Priority 1) Yes No N/A

6.3 Ensure that pages are usable when scripts, applets, or other programmatic objects are turned  
off or not supported. If this is not possible, provide equivalent information on an alternative 
accessible page. 

    x

And if you use multimedia (Priority 1) Yes No N/A

1.3 Until user agents can automatically read aloud the text equivalent of a visual track, provide an 
auditory description of the important information of the visual track of a multimedia presentation. 

    x

1.4 For any time-based multimedia presentation (e.g., a movie or animation), synchronize equivalent 
alternatives (e.g., captions or auditory descriptions of the visual track) with the presentation. 

    x

And if all else fails (Priority 1) Yes No N/A

11.4 If, after best efforts, you cannot create an accessible page, provide a link to an alternative 
page that uses W3C technologies, is accessible, has equivalent information (or functionality), and is 
updated as often as the inaccessible (original) page. 

x     



34   inFoRmation tEcHnoLoGY anD LiBRaRiEs  |  sEptEmBER 2008

Priority 2 checkpoints

In General (Priority 2) Yes No N/A

2.2 Ensure that foreground and background color combinations provide sufficient contrast when 
viewed by someone having color deficits or when viewed on a black and white screen. [Priority 2 
for images, Priority 3 for text.] 

x2     

3.1 When an appropriate markup language exists, use markup rather than images to convey 
information. 

x3     

3.2 Create documents that validate to published formal grammars. x     

3.3 Use style sheets to control layout and presentation. x4     

3.4 Use relative rather than absolute units in markup language attribute values and style sheet 
property values. 

  x    

3.5 Use header elements to convey document structure and use them according to specification. x     

3.6 Mark up lists and list items properly. x     

3.7 Mark up quotations. Do not use quotation markup for formatting effects such  
as indentation. 

x     

6.5 Ensure that dynamic content is accessible or provide an alternative presentation or page.     x 

7.2 Until user agents allow users to control blinking, avoid causing content to blink (i.e., change 
presentation at a regular rate, such as turning on and off). 

    x

7.4 Until user agents provide the ability to stop the refresh, do not create periodically auto-
refreshing pages. 

    x

7.5 Until user agents provide the ability to stop auto-redirect, do not use markup to redirect pages 
automatically. Instead, configure the server to perform redirects. 

    x

10.1 Until user agents allow users to turn off spawned windows, do not cause pop-ups or other 
windows to appear and do not change the current window without informing the user. 

    x

11.1 Use W3C technologies when they are available and appropriate for a task and use the latest 
versions when supported. 

    x

11.2 Avoid deprecated features of W3C technologies.     x

12.3 Divide large blocks of information into more manageable groups where natural and 
appropriate. 

x     

13.1 Clearly identify the target of each link. x     

13.2 Provide metadata to add semantic information to pages and sites. x     

13.3 Provide information about the general layout of a site (e.g., a site map or table  
of contents). 

x     

13.4 Use navigation mechanisms in a consistent manner. x     



aRE pDF DocumEnts accEssiBLE?  |  RiBERa tuRRó   35

In General (Priority 2), cont. Yes No N/A

And if you use tables (Priority 2) Yes No N/A

5.3 Do not use tables for layout unless the table makes sense when linearized. Otherwise, if the 
table does not make sense, provide an alternative equivalent (which may be a linearized version). 

x     

5.4 If a table is used for layout, do not use any structural markup for the purpose of visual 
formatting. 

x     

And if you use frames (Priority 2) Yes No N/A

12.2 Describe the purpose of frames and how frames relate to each other if it is not obvious by 
frame titles alone. 

    x

And if you use forms (Priority 2) Yes No N/A

10.2 Until user agents support explicit associations between labels and form  
controls, for all form controls with implicitly associated labels, ensure that the label  
is properly positioned. 

x     

12.4 Associate labels explicitly with their controls. x     

And if you use applets and scripts (Priority 2) Yes No N/A

6.4 For scripts and applets, ensure that event handlers are input-device independent.     x

7.3 Until user agents allow users to freeze moving content, avoid movement in pages.     x

8.1 Make programmatic elements such as scripts and applets directly accessible or compatible 
with assistive technologies. [Priority 1 if functionality is important and not presented elsewhere, 
otherwise Priority 2.] 

    x

9.2 Ensure that any element that has its own interface can be operated in a device-independent 
manner. 

    x

9.3 For scripts, specify logical event handlers rather than device-dependent  
event handlers. 

    x

Priority 3 checkpoints

In General (Priority 3) Yes No N/A

4.2 Specify the expansion of each abbreviation or acronym in a document where it first occurs.  x5     

4.3 Identify the primary natural language of a document. x     

9.4 Create a logical tab order through links, form controls, and objects. x     

9.5 Provide keyboard shortcuts to important links (including those in client-side image maps), form 
controls, and groups of form controls. 

  x6   

10.5 Until user agents (including assistive technologies) render adjacent links distinctly, include non-
link, printable characters (surrounded by spaces) between adjacent links. 

x     

11.3 Provide information so that users may receive documents according to their preferences (e.g., 
language, content type, etc.).

    x



36   inFoRmation tEcHnoLoGY anD LiBRaRiEs  |  sEptEmBER 2008

In General (Priority 3), cont. Yes No N/A

13.5 Provide navigation bars to highlight and give access to the  
navigation mechanism. 

    x

13.6 Group related links, identify the group (for user agents), and, until user agents do so, provide a 
way to bypass the group. 

x     

13.7 If search functions are provided, enable different types of searches for different skill levels and 
preferences. 

x7     

13.8 Place distinguishing information at the beginning of headings, paragraphs,  
lists, etc. 

x     

13.9 Provide information about document collections (i.e., documents comprising multiple pages). x     

13.10 Provide a means to skip over multi-line ASCII art. x     

14.2 Supplement text with graphic or auditory presentations where they will facilitate comprehension 
of the page. 

x     

14.3 Create a style of presentation that is consistent across pages. x     

And if you use images and image maps (Priority 3) Yes No N/A

1.5 Until user agents render text equivalents for client-side image map links, provide redundant text 
links for each active region of a client-side image map. 

    x

And if you use tables (Priority 3) Yes No N/A

5.5 Provide summaries for tables.  x8     

5.6 Provide abbreviations for header labels. x     

10.3 Until user agents (including assistive technologies) render side-by-side text correctly, provide 
a linear text alternative (on the current page or some other) for all tables that lay out text in parallel, 
word-wrapped columns. 

x     

And if you use forms (Priority 3) Yes No N/A

10.4 Until user agents handle empty controls correctly, include default, place-holding characters in 
edit boxes and text areas. 

x    

Notes

 1. This information is not correctly transferred from some 
word processors to the PDF format.

 2. Adobe Reader allows color combinations in text to  
be changed.

 3.  The PDF tag set is very limited and does not include mat-
hematical formulas or chemical symbols.

 4. The latest versions of PDF use CSS.
 5. Creators can use the E element to specify an abbreviation  

for a word.
 6. Adobe Reader and Adobe Acrobat use generic access 

keys, but they cannot be specified in a document.
 7. Included in Adobe Reader and Adobe Acrobat.
 8. Only as of version 1.7.



aRE pDF DocumEnts accEssiBLE?  |  RiBERa tuRRó   37

APPENDIx B. WCAG 2.0 checklist of checkpoints (draft April 2006)

Principle 1: Content must be perceivable

Guideline 1.1: Provide text alternatives for all non-text content Yes No N/A

Level 1 Success Criteria for Guideline 1.1

For all non-text content, one of the following is true:

If non-text content presents information or responds to user input, text alternatives serve the same 
purpose and present the same information as the non-text content. If text alternatives cannot serve 
the same purpose, then text alternatives at least identify the purpose of the non-text content.

If non-text content is multimedia; live audio-only or live video-only content; a test or exercise that 
must use a particular sense; or primarily intended to create a specific sensory experience; then text 
alternatives at least identify the non-text content with a descriptive text label. 

If the purpose of non-text content is to confirm that content is being operated by a person rather 
than a computer, different forms are provided to accommodate  
multiple disabilities.

If non-text content is pure decoration, or used only for visual formatting, or if it is not presented to 
users, it is implemented such that it can be ignored by assistive technology.

x1

Guideline 1.2 Provide synchronized alternatives for multimedia  
(not analyzed in this article)

Yes No N/A

Level 1 Success Criteria for Guideline 1.2

1.2.1 Captions are provided for prerecorded multimedia. 

1.2.2 Audio descriptions of video, or a full multimedia text alternative including any interaction, are 
provided for prerecorded multimedia. 

Level 2 Success Criteria for Guideline 1.2 

1.2.3 Audio descriptions of video are provided for prerecorded multimedia. 

1.2.4 Captions are provided for live multimedia. 

Level 3 Success Criteria for Guideline 1.2 

1.2.5 Sign-language interpretation is provided for multimedia. 

1.2.6 Extended audio descriptions of video are provided for  
prerecorded multimedia. 

1.2.7 For prerecorded multimedia, a full multimedia text alternative including any interaction is 
provided. 

Guideline 1.3: Ensure that information and structure can be separated  
from presentation

Yes No N/A

Level 1 Success Criteria for Guideline 1.3

1.3.1 Information and relationships conveyed through presentation can be programmatically 
determined, and notification of changes to these is available to user agents, including assistive 
technologies. 

x

1.3.2 Any information that is conveyed by color is also visually evident  
without color. 

x



38   inFoRmation tEcHnoLoGY anD LiBRaRiEs  |  sEptEmBER 2008

Guideline 1.3: Ensure that information and structure can be separated  
from presentation, cont.

Yes No N/A

1.3.3 When the sequence of the content affects its meaning, that sequence can be 
programmatically determined. 

x

Level 2 Success Criteria for Guideline 1.3 

1.3.4 Information that is conveyed by variations in presentation of text is also conveyed in text, or 
the variations in presentation of text can be programmatically determined. 

x

1.3.5 Information required to understand and operate content does not rely on shape, size, visual 
location, or orientation of components. 

x

Guideline 1.4: Make it easy to distinguish foreground information from its background Yes No N/A

Level 2 Success Criteria for Guideline 1.4

1.4.1 Text or diagrams, and their background, have a luminosity contrast ratio of at least 5:1. x

1.4.2 A mechanism is available to turn off background audio that plays automatically, without 
requiring the user to turn off all audio. 

x

Level 3 Success Criteria for Guideline 1.4 

1.4.3 Text or diagrams, and their background, have a luminosity contrast ratio of at least 10:1. x

1.4.4 Audio content does not contain background sounds, background sounds can be turned off, 
or background sounds are at least 20 decibels lower than the foreground audio content, with the 
exception of occasional sound effects. 

x

Principle 2: Interface components in the content must be operable

Guideline 2.1: Make all functionality operable via a keyboard interface Yes No N/A

Level 1 Success Criteria for Guideline 2.1

2.1.1 All functionality of the content is operable in a non-time-dependent  
manner through a keyboard interface, except where the task requires analog, time-dependent 
input.

Note: This does not preclude and should not discourage the support of other input methods (such 
as a mouse) in addition to keyboard operation.

x

Level 3 Success Criteria for Guideline 2.1 

2.1.2 All functionality of the content is operable in a non-time-dependent manner through a 
keyboard interface. 

x



aRE pDF DocumEnts accEssiBLE?  |  RiBERa tuRRó   39

Guideline 2.2: Allow users to control time limits on their reading or interaction Yes No N/A

Level 1 Success Criteria for Guideline 2.2

2.2.1 For each time-out that is a function of the content, at least one of the following  
is true: 

• the user is allowed to deactivate the time-out; or

•  the user is allowed to adjust the time-out over a wide range that is at least ten times the length of 
the default setting; or

•  the user is warned before time expires and given at least 20 seconds to extend the time-out with 
a simple action (for example, “hit any key”), and the user is allowed to extend the timeout at least 
ten times; or

•  the time-out is an important part of a real-time event (for example, an auction), and no alternative 
to the time-out is possible; or

•  the time-out is part of an activity where timing is essential (for example, competitive gaming or 
time-based testing) and time limits can not be extended further without invalidating the activity.

x

Level 2 Success Criteria for Guideline 2.2 

2.2.2 Content does not blink for more than three seconds, or a method is available to stop all 
blinking content in the Web unit or authored component. 

x

2.2.3 Content can be paused by the user unless the timing or movement is part of an activity where 
timing or movement is essential. 

x

Level 3 Success Criteria for Guideline 2.2 

2.2.4 Except for real-time events, timing is not an essential part of the event or activity presented 
by the content. 

x

2.2.5 Interruptions, such as updated content, can be postponed or suppressed by the user, except 
interruptions involving an emergency. 

x

2.2.6 When an authenticated session expires, the user can continue the activity without loss of 
data after re-authenticating. 

x

Guideline 2.3: Allow users to avoid content that could cause seizures  
due to photosensitivity

Yes No N/A

Level 1 Success Criteria for Guideline 2.3

2.3.1 Content does not violate the general flash threshold or the red flash threshold. x

Level 3 Success Criteria for Guideline 2.3 

2.3.2 Web units do not contain any components that flash more than three times in any one-
second period. 

x



40   inFoRmation tEcHnoLoGY anD LiBRaRiEs  |  sEptEmBER 2008

Guideline 2.4: Provide mechanisms to help users find content, orient themselves within it, 
and navigate through it

Yes No N/A

Level 1 Success Criteria for Guideline 2.4

2.4.1 A mechanism is available to bypass blocks of content that are repeated on multiple Web 
units. 

x

Level 2 Success Criteria for Guideline 2.4

2.4.2 More than one way is available to locate content within a set of Web units where content is 
not the result of, or a step in, a process or task. 

x

2.4.3 Web units have titles. x

2.4.4 Each link is programmatically associated with text from which its purpose can  
be determined. 

x

Level 3 Success Criteria for Guideline 2.4 

2.4.5 Titles, headings, and labels are descriptive. x

2.4.6 When a Web unit or authored component is navigated sequentially, components receive 
focus in an order that follows relationships and sequences in the content. 

x

2.4.7 Information about the user’s location within a set of Web units is available. x

2.4.8 The purpose of each link can be programmatically determined from the link. x

Guideline 2.5: Help users avoid mistakes and make it easy to correct mistakes  
that do occur

Yes No N/A

Level 1 Success Criteria for Guideline 2.5

2.5.1 If an input error is detected, the error is identified and described to the user  
in text. 

x

Level 2 Success Criteria for Guideline 2.5

2.5.2 If an input error is detected and suggestions for correction are known and can be provided 
without jeopardizing the security or purpose of the content, the suggestions are provided to the 
user. 

x

2.5.3 For forms that cause legal or financial transactions to occur, that modify or delete data in 
data storage systems, or that submit test responses, at least one of the following is true:

Actions are reversible.

Actions are checked for input errors before going on to the next step in the process.

The user is able to review and confirm or correct information before submitting it.

x

Level 3 Success Criteria for Guideline 2.5 

2.5.4 Context-sensitive help is available for text input. x

Principle 3: Content and controls must be understandable

Guideline 3.1: Make text content readable and understandable Yes No N/A

Level 1 Success Criteria for Guideline 3.1

3.1.1 The primary natural language or languages of the Web unit can be programmatically 
determined.

x2

Level 2 Success Criteria for Guideline 3.1 



aRE pDF DocumEnts accEssiBLE?  |  RiBERa tuRRó   41

Guideline 3.1: Make text content readable and understandable, cont. Yes No N/A

3.1.2 The natural language of each passage or phrase in the Web unit can be programmatically 
determined 

Note: This requirement does not apply to individual words or phrases that have become part of 
the primary language of the content.

x2

Level 3 Success Criteria for Guideline 3.1 

3.1.3 A mechanism is available for identifying specific definitions of words or phrases used in an 
unusual or restricted way, including idioms and jargon. 

x3

3.1.4 A mechanism for finding the expanded form of abbreviations is available. x4

3.1.5 When text requires reading ability more advanced than the lower secondary education level, 
supplemental content is available that does not require reading ability more advanced than the 
lower secondary education level. 

x

3.1.6 A mechanism is available for identifying specific pronunciation of words where meaning 
cannot be determined without pronunciation. 

x3

Guideline 3.2: Make the placement and functionality of content predictable Yes No N/A

Level 1 Success Criteria for Guideline 3.2

3.2.1 When any component receives focus, it does not cause a change of context. x

3.2.2 Changing the setting of any form control or field does not automatically cause a change 
of context (beyond moving to the next field in tab order), unless the authored unit contains 
instructions before the control that describe the behavior. 

x

Level 2 Success Criteria for Guideline 3.2

3.2.3 Navigational mechanisms that are repeated on multiple Web units within a set of Web units 
or other primary resources occur in the same relative order each time they are repeated, unless a 
change is initiated by the user. 

x

3.2.4 Components that have the same functionality within a set of Web units are identified 
consistently. 

x

Level 3 Success Criteria for Guideline 3.2 

3.2.5 Changes of context are initiated only by user request. x

Principle 4: Content should be robust enough to work with current and future user agents  
(including assistive technologies)

Guideline 4.1: Support compatibility with current and future user agents  
(including assistive technologies)

Yes No N/A

Level 1 Success Criteria for Guideline 4.1

4.1.1 Web units or authored components can be parsed unambiguously, and the relationships in 
the resulting data structure are also unambiguous. 

x

4.1.2 For all user interface components, the name and role can be programmatically determined, 
values that can be set by the user can be programmatically set, and notification of changes to 
these items is available to user agents, including  
assistive technologies.

x



42   inFoRmation tEcHnoLoGY anD LiBRaRiEs  |  sEptEmBER 2008

Guideline 4.2: Ensure that content is accessible or provide an accessible alternative Yes No N/A

Level 1 Success Criteria for Guideline 4.2

4.2.1 At least one version of the content meets all Level 1 success criteria, but alternate version(s) 
that do not meet all Level 1 success criteria may be available from the same URI. 

x

4.2.2 Content meets the following criteria even if the content uses a technology that is not in the 
chosen baseline: If content can be entered using the keyboard, then the content can be exited 
using the keyboard. Content conforms to success criterion 2.3.1 (general and red flash).

x 

Level 2 Success Criteria for Guideline 4.2 

4.2.3 At least one version of the content meets all Level 2 success criteria, but alternate version(s) 
that do not meet all Level 2 success criteria may be available from the same URI. 

x

Level 3 Success Criteria for Guideline 4.2 

4.2.4 Content implemented using technologies outside of the chosen baseline satisfies all Level 1 
and Level 2 requirements supported by the technologies. 

x

Notes

 1.  Nonfunctional content can be specified using watermarks, 
or can simply be deleted from the reading order or the tag tree.

 2. This information is not correctly transferred from some 
word processors to the PDF format.

 3.  Creators can use the title attribute to specify an alternate 
title for a tag.

 4.  Creators can use the E element to specify the abbreviation 
for a word.



aRE pDF DocumEnts accEssiBLE?  |  RiBERa tuRRó   43

APPENDIx C. Section 508 checklist

Section 508 PASS FAIL N/A

(a) A text equivalent for every non-text element shall be provided (e.g., via “alt,” “longdesc,” or 
in element content).

x

(b) Equivalent alternatives for any multimedia presentation shall be synchronized with the 
presentation. 

x

(c) Webpages shall be designed so that all information conveyed with color is also available 
without color, for example from context or markup.

x

(d) Documents shall be organized so they are readable without requiring an associated style 
sheet.

x

(e) Redundant text links shall be provided for each active region of a server-side image map. x

(f) Client-side image maps shall be provided instead of server-side image maps except where 
the regions cannot be defined with an available geometric shape.

x

(g) Row and column headers shall be identified for data tables. x

(h) Markup shall be used to associate data cells and header cells for data tables that have two 
or more logical levels of row or column headers.

x

(i) Frames shall be titled with text that facilitates frame identification  
and navigation.

x

(j) Pages shall be designed to avoid causing the screen to flicker with a frequency greater than 
2 Hz and lower than 55 Hz.

x

(k) A text-only page, with equivalent information or functionality, shall be provided to make a 
website comply with the provisions of this part, when compliance cannot be accomplished in 
any other way. The content of the text-only page shall be updated whenever the primary page 
changes.

x

(l) When pages utilize scripting languages to display content, or to create interface elements, 
the information provided by the script shall be identified  
with functional text that can be read by assistive technology. [Not evaluated in this article]

x

(m) When a webpage requires that an applet, plug-in, or other application be present on the 
client system to interpret page content, the page must provide a link to a plug-in or applet that 
complies with §1194.21(a) through (l).

x

(n) When electronic forms are designed to be completed online, the form shall allow people 
using assistive technology to access the information, field elements, and functionality required 
for completion and submission of the form, including all directions and cues.

x

(o) A method shall be provided that permits users to skip repetitive  
navigation links.

x

(p) When a timed response is required, the user shall be alerted and given sufficient time to 
indicate more time is required.

x