Achieving WCAG 2.0 with PDF/UA

Table of Contents

Introduction

Many organizations are tasked with implementing accessibility in their electronic content and related applications through adoption of the W3C's Web Content Accessibility Guidelines 2.0 (WCAG 2.0). WCAG 2.0, however, was written with Web content in mind and to be technically neutral in its prescriptions for Web technology. The application of WCAG 2.0 to other electronic content technologies, especially technologies that are not essentially of the Web, requires interpretation to determine how to apply WCAG 2.0 Principles, Guidelines and Success Criteria. There are instances in which a 1:1 mapping does not exist, and in many cases, such as in PDF, it is generally appropriate to consult the accessibility standard (if any) developed specifically for that technology.

Version

This document is designated version 1.01 with a release date of August 16, 2012. A change history will be maintained in future revisions.

Caution Regarding Versions of ISO 14289-1:2012

ISO-14289-1:2012 is now available from ISO and partner organizations such as ANSI.

Those with pre-publication versions are advised that the published version contains final corrections to the FDIS. Be sure your copy of PDF/UA includes a Corrected Version date of 2012-08-01 on the cover.

Ownership

While WCAG 2.0 is freely available online PDF/UA is a copyrighted publication of the ISO. The document may be purchased from the ISO online store or from national standards bodies such as or ANSI in the United States.

This document, "Achieving WCAG 2.0 with PDF/UA", is a publication of AIIM. The document is produced and maintained by AIIM's US Committee for PDF/UA, the original author of ISO 14289. Reuse and reposting of this document is encouraged. Any such usage must include attribution to AIIM and a link to this page. 

Purpose

This document articulates the alignment between WCAG 2.0 and ISO 14289-1:2012 (PDF/UA), the international standard for accessible PDF technology. PDF software developers can achieve conformance with applicable WCAG 2.0 Success Criteria via implementations that follow this mapping to PDF/UA. As such, this mapping shows how to validate, in PDF file-format terms, a PDF/UA document against WCAG 2.0.

Background

PDF technology was invented long before the Web became a general utility. The format became popular worldwide because PDF offers a reliable and portable electronic document format, however, PDF as originally designed did not include accessibility - or any sort of reuse - as a consideration. While the current PDF Reference (ISO 32000-1:2008) describes accessibility mechanisms for PDF content added largely in versions 1.3 and 1.4 of the PDF Reference. Those descriptions - as a perusal of W3C's own 2008 report on ISO 32000-1 reveals - are incomplete and unclear. As a result, and notwithstanding the worldwide popularity and widespread dependence on PDF, industry and end-user support for the accessibility features added to PDF in 2000 has remained weak.

Published as an International Standard in 2012, ISO 14289-1:2012 (PDF/UA) was initiated by AIIM and Adobe Systems in 2004 to provide clear normative terms for achieving accessibility in the PDF format.

PDF/UA includes three key sections of requirements. Section 7 is dedicated to the file-format itself while Section 8 is dedicated to PDF reader software. Section 9 is directed at assistive technologies (AT) delivering the reader software's output to the user.

Admonition

PDF/UA is the normative technical standard that provides a consistent means of achieving accessibility using PDF technology. PDF/UA specifies technical requirements for conforming PDF files, PDF readers and PDF-consuming assistive technology. The document does not state general accessibility principles, nor does it specifically address the application of WCAG 2.0 to PDF files. 

PDF/UA and WCAG 2.0 are complementary with no conflicts. Conformance with one, however, does not guarantee conformance with the other. For some Success Criteria, notably those concerning media, actions, scripting, design or content considerations, authors and software developers must refer directly to WCAG 2.0. 

EXAMPLE: WCAG 2.0 Success Criteria 1.2.1 requires that:

"Either an alternative for time-based media or an audio track is provided that presents equivalent information for prerecorded video-only content."

In the case of media, PDF/UA simply requires that video or audio clips embedded in a conforming PDF file are tagged with an alternative description and that a certain key value be present. PDF/UA does not prescribe how "equivalent information" is to be delivered in PDF files containing such media clips. To comply with Success Criterion 1.2.1 in PDF, therefore, an author or developer must determine either that the alternative description provided in the PDF file for a media clip constitutes "equivalent information" or that "equivalent information" is provided in some other way.

WCAG 2.0 Requirements Beyond PDF/UA

WCAG 2.0 provides guidelines for general web content and is thus far broader in scope than PDF/UA. In some cases, therefore, PDF/UA conformance alone cannot assure conformance with WCAG 2.0 and direct reference to the WCAG 2.0 Guidelines is required.

The following list explains terms used in the Achieving WCAG 2.0 with PDF/UA table to help identify cases in which a WCAG 2.0 conformance claim cannot use PDF/UA alone to conform to WCAG 2.0 but requires validation against WCAG 2.0 directly in addition to applicable PDF/UA requirements.

  • Time-based media alternatives, test, sensory and CAPTCHAs.  PDF/UA does not address these items. Refer to WCAG 2.0.
  • Audio and/or Video content. PDF/UA includes syntactical requirements but does not address the actual audio and video content. Refer to WCAG 2.0.
  • Video captions. PDF/UA does not address video captions. Refer to WCAG 2.0.
  • JavaScript design. While identifying some requirements for accessible scripting with PDF technology, PDF/UA is not a JavaScript accessibility standard. Refer to WCAG 2.0.
  • JavaScript or Media content. As above, PDF/UA is not a JavaScript or multimedia accessibility standard. Refer to WCAG 2.0.
  • Control device specific. PDF/UA is control device-independent. Refer to WCAG 2.0.
  • Design consideration. In general, PDF/UA does not address visual appearance, content or design choices and relies on semantic equivalents. Refer to WCAG 2.0.
  • Dynamic XFA-PDF. While prohibited in PDF/UA, dynamic XFA-PDF is not prohibited by WCAG 2.0.

PDF/UA Requirements Unaddressed in WCAG 2.0

In a few cases PDF/UA includes key objectives or requirements with no precise or near-equivalent in WCAG 2.0. These cases include:

  • Interoperability (consistency and reliability). PDF is distinguished from other formats by the fact that reliable, consistent rendering (content delivery) irrespective of consuming software (viewers, printers, assistive technology, etc) is its key value proposition. Both operationally and economically, a high degree of interoperability is as vital to equal access to PDF content as reliable rendering is critical to PDF's value on-screen and in-print. WCAG 2.0 does not normatively address interoperability.
    PDF/UA is a classical interoperability-oriented technology standard. A fundamental design objective was the creation of normative requirements for ensuring accessibility-related features are maximally interoperable.
  • Fonts. Font substitutions can result in compromised legibility for any user, and especially for cognitively impaired and dyslexic users. WCAG 2.0 addresses fonts to some extent via SC 1.4.5 but has no provisions regarding fidelity to source content, legibility problems occasioned by mismanagement of fonts or the specific use of fonts to suit accessibility purposes.
    PDF/UA 7.21 requires embedded fonts to ensure the accurate conveyance of the author's intent with the highest degree of legibility.
  • Headings as Navigation. In the vast majority of PDF files (as well as in other file formats), headings (H1, H2, H3, etc.) are the only feature providing equivalent intra-document navigation for AT users. WCAG 2.0 does not address the navigational role of headings nor does WCAG 2.0 require that headings be logically structured.
    PDF/UA 7.4 requires
    that headings are logically structured to enable navigation. 
  • Article Threads. No longer frequently used, the PDF article threads feature is a quick-and-dirty way of providing a window-width view that automatically scrolls forward with each click. Tagged PDF readers may deliver this same functionality today using the tags tree, if desired. WCAG 2.0 does not address this feature.
    PDF/UA 7.12 requires that if present, article threads shall follow the logical structure (tags) of the document. 

Achieving WCAG 2.0 Conformance with PDF/UA

The 61 WCAG 2.0 Success Criteria are presented in the following table. For each Criterion, the table indicates applicable subsection(s) of PDF/UA for (respectively) conforming files and reader software. As a convenience for developers, all corresponding references to ISO 32000-1 are also provided.

WCAG 2.0 ISO 14289-1 (File) ISO 14289-1 (Reader) ISO 32000-1 Requirements beyond PDF/UA
1.1.1 Non-text Content. (A) 7.3 addresses content requiring text alternatives. 
7.18.1 paragraph 4 addresses control descriptions.
7.1 paragraph 1 addresses decoration.
8.1 14.8.4.5 
14.9.3
 
Time-based media alternatives, test, sensory and CAPTCHA
1.2.1 Audio-only and Video-only (Prerecorded). (A) 7.11 
7.18.6.2 
7.18.7 
8.11.3 7.11.3 
13.2.4.2
Audio & video content
1.2.2 Captions (Prerecorded). (A) 7.11 
7.18.6.2 
7.18.7 
8.11.3  7.11.3 
13.2.4.2
Video captions
1.2.3 Audio Description or Media Alternative (Prerecorded). (A) 7.11 
7.18.6.2 
7.18.7 
8.11.3  7.11.3 
13.2.4.2
Audio & video content
1.2.4 Captions (Live). (AA) 7.18.6.2  8.11.3  7.11.3 
13.2.4.2
Video captions
1.2.5 Audio Description (Prerecorded). (AA) 7.11 
7.18.6.2 
7.18.7 
8.11.3  7.11.3 
13.2.4.2
Audio content
1.2.6 Sign Language (Prerecorded). (AAA) 7.11 
7.18.6.2 
7.18.7 
8.11.3  7.11.3 
13.2.4.2
Video content
1.2.7 Extended Audio Description (Prerecorded). (AAA) 7.11 
7.18.6.2 
7.18.7
8.11.3  7.11.3 
13.2.4.2
Audio content
1.2.8 Media Alternative (Prerecorded).  (AAA) 7.11 
7.18.6.2 
7.18.7 
8.11.3  7.11.3 
13.2.4.2
Audio & video content
1.2.9 Audio-only (Live). (AAA) 7.11 
7.18.6.2
8.11.3  7.11.3 
13.2.4.2
Audio content
1.3.1 Info and Relationships. (Level A) 7.1 
7.2 
7.3 
7.4.1 * 
7.5 
7.6 
7.7 
7.8 
7.9 
7.10 
7.20 & above address content 
7.17 & 
7.18 address annotations
8.1 7.7.2 
7.7.3.3 

7.9.2 
8.11.2.1 
8.11.4.5 
9.10.2 

12.2 
12.3.3 
12.5.6.5 
12.5.6.15 

12.6 
13.2.4.2 

14.7.2 
14.8 
14.9.2 
14.9.3 
14.9.4
 -
1.3.2 Meaningful Sequence. (Level A)  7.2 8.2 paragraph 1 7.9.2 
14.8.2.4.2 
14.9.2 
14.9.4 
 -
1.3.3 Sensory Characteristics. (Level A) 7.1 paragraph 6 and 7 -  -  -
1.4.1 Use of Color. (Level A) 7.1 paragraph 6 references WCAG 2.0 1.4 directly -  - Design Consideration
1.4.2 Audio Control. (Level A) Not Applicable 8.10.3   -  -
1.4.3 Contrast (Minimum). (Level AA) 7.1 paragraph 6 references WCAG 2.0 1.4 directly -  - Design Consideration
1.4.4 Resize text. (Level AA)  7.2 - 7.9.2 
14.8.2.4.2 
14.9.2 
14.9.4 
 -
1.4.5 Images of Text. (Level AA) 7.3 paragraph 6 -  -  -
1.4.6 Contrast (Enhanced). (Level AAA) 7.1 paragraph 6 references WCAG 2.0 1.4 directly  - Design Consideration
1.4.7 Low or No Background Audio. (Level AAA) Content consideration -  - Audio content
1.4.8 Visual Presentation. (Level AAA) Content consideration -  - Graphic design
1.4.9 Images of Text (No Exception). (Level AAA)  Content consideration -  - Graphic design
2.1.1 Keyboard. (Level A)  Content consideration.
7.19, paragraph 3 addresses timing. 
8.1 paragraph 2, bullets 3 and 4 12.6  Control device specific
2.1.2 No Keyboard Trap. (Level A) Content consideration  8.7   - JavaScript design
2.1.3 Keyboard (No Exception). (Level AAA) Content consideration. 
7.19, paragraph 3 addresses timing.
8.1 paragraph 2, bullet 3, and 4 12.6  Control device specific
2.2.1 Timing Adjustable. (Level A) 7.19, paragraph 3  8.10.3 paragraphs 2 and 3 12.6 Media content
2.2.2 Pause, Stop, Hide. (Level A) Content consideration  8.6 
8.7 
8.10.3 
12.6 JavaScript or media content
2.2.3 No Timing. (Level AAA) 7.19  8.7 12.6 JavaScript or media content
2.2.4 Interruptions. (Level AAA) 7.19  8.7 12.6 JavaScript or media content
2.2.5 Re-authenticating. (Level AAA) 7.19  12.6 JavaScript design
2.3.1 Three Flashes or Below Threshold. (Level A) 7.1, paragraph 5  -  -
2.3.2 Three Flashes.(Level AAA) 7.1, paragraph 5 -  -  -
2.4.1 Bypass Blocks. (Level A)  7.4 
7.8 
7.1 paragraphs 1 and 2
8.9 bullet 2 14.8  -
2.4.2 Page Titled. (Level A)  7.1 paragraphs 8 and 9 8.8 12.2  -
2.4.3 Focus Order. (Level A)  7.1 paragraph 2 
7.18.1 paragraph 2 
7.18.3
8.1 
8.9
14.8.4.4.3  -
2.4.4 Link Purpose (In Context). (Level A) 7.18.1 paragraph 2 
7.18.5
8.1 12.5.6.5 
12.6.4.7 
14.8.4.4.3 
14.9.3
 -
2.4.5 Multiple Ways. (Level AA)  7.17 
7.18.5
8.9 12.3.3 
12.5.6.5 
12.6.4.7 
Table 28 
14.9.3 
 -
2.4.6 Headings and Labels. (Level AA)  Content consideration -  - Design consideration
2.4.7 Focus Visible. (Level AA)  Out of scope -  - Design consideration
2.4.8 Location. (Level AAA)  Out of scope -  - Design consideration
2.4.9 Link Purpose (Link Only). (Level AAA)  7.18.5 paragraph 2 8.10.1 14.9.3 Design consideration
2.4.10 Section Headings. (Level AAA) Out of scope 8.9, bullet 2 14.8.4.3.2 
14.8.4.3.5
Design consideration
3.1.1 Language of Page. (Level A)  7.2 paragraph 3 8.2, paragraph 3  -  -
3.1.2 Language of Parts. (Level AA)  7.2 paragraph 3 8.2, paragraphs 2 and 3  -  -
3.1.3 Unusual Words. (Level AAA) Out of scope  -  - Design consideration
3.1.4 Abbreviations. (Level AAA) Out of scope **  - Design consideration
3.1.5 Reading Level. (Level AAA) Out of scope -  - Design consideration
3.1.6 Pronunciation. (Level AAA) Out of scope -  - Design consideration
3.2.1 On Focus. (Level A) 7.19 paragraph 2 8.7  - Design consideration
3.2.2 On Input. (Level A) 7.19 paragraph 2 8.7  - Design consideration
3.2.3 Consistent Navigation. (Level AA)  Design consideration -  - Design consideration
3.2.4 Consistent Identification. (Level AA) Design consideration -  - Design consideration
3.2.5 Change on Request. (Level AAA)  Design consideration -  - JavaScript consideration
3.3.1 Error Identification. (Level A) Design consideration 8.7  - JavaScript consideration
3.3.2 Labels or Instructions. (Level A)  7.18.1 
7.18.3 
7.18.4
8.10.2 14.8.4.4.3 
14.9.3 
14.8.4.5 
 -
3.3.3 Error Suggestion (Level AA) Design consideration 8.10.2  - Design consideration
3.3.4 Error Prevention (Level AA) Design consideration 8.10.2  - Design consideration
3.3.5 Help: Context-sensitive help is available. (Level AAA) Out of scope -  - Design consideration
3.3.6 Error Prevention (Level AAA) Design consideration -  - Design consideration
4.1.1 Parsing (Level A)  Not applicable -  - Dynamic XFA-PDF only
4.1.2 Name, Role, Value (Level A)  7.13 
7.14 
7.18
8.10 
8.11.2 
 -  -

Notes

* - Since headings are a key means of navigating PDF files for users relying on assistive technology PDF/UA requires logical heading levels for conformance.

** - Developers should consider supporting the "E" property in Marked Content. See ISO 32000-1, 14.9.5.

Failing WCAG 2.0 Conformance with PDF/UA

Violating PDF/UA (except with respect to the PDF/UA XMP metadata flag itself) should be considered a violation of WCAG 2.0. The only exceptions are PDF/UA 7.4.2. 7.4.3, 7.4.4 and 7.12, none of which are required by WCAG 2.0.

References

Accessibility Guidelines & Standards

Other Support & Informative Documents

Change History

2012-08-16

  • SC 1.3.1 - 7.4 changed to 7.4.1. Failing Conformance statement updated to match.
  • Version 1.0 published