Achieving WCAG 2.0 with PDF/UA v0.983 (release-candidate)
NOTICE: This document is not for distribution until authorized by the US Committee for PDF/UA and AIIM's Standards Committee.
Table of Contents
- Introduction
- Ownership
- Background
- Purpose
- Admonition
- Notes to the Mapping
- Achieving WCAG 2.0 with PDF/UA
- Footnotes
- References
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 and Success Criteria. There are instances in which a 1:1 mapping does not exist, and in many cases, such as in PDF, it may be most appropriate to consult the standard written specifically for that technology.
Ownership
A publication of AIIM, this document is produced and maintained by AIIM's US Committee for PDF/UA, the original author of PDF/UA. Reuse and reposting of this document is encouraged, but any such usage must include attribution to AIIM and a link to this page.
While WCAG 2.0 is freely available online, PDF/UA, formally known as ISO 14289, an International Standard published by the ISO, is not. PDF/UA may be purchased online directly from ISO or following publication, from ANSI.
Background
PDF technology was invented long before the Web became a general utility. While the current PDF Reference (ISO 32000-1:2008) describes accessibility mechanisms for PDF content, that description - as a perusal of W3C's 20008 report on ISO 32000 makes clear - is incomplete.
AIIM's PDF/UA project began, among other reasons, as a response to these gaps in the PDF Reference.
Purpose
This document articulates the alignment between the Web Content Accessibility Guidelines 2.0 (WCAG 2.0) and ISO 14289-1:2012 (PDF/UA). 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.
Admonition
PDF/UA is the normative technical accessibility standard specific to the PDF file format. PDF/UA does not state accessibility principles nor does it specifically address the application of WCAG 2.0 to PDF files. PDF/UA is strictly limited to PDF file-format and conforming PDF reader and AT requirements for universally accessible PDF files within the limitations of the PDF format and other applicable standards.
PDF/UA and WCAG 2.0 are complementary with no conflicts. Conformance with one, however, does not guarantee conformance with the other. PDF files may contain media, actions, scripts and content requiring consideration beyond the scope of PDF/UA in order to conform with WCAG 2.0.
For each WCAG 2.0 Success Criterion applicable to PDF syntax, this mapping identifies the matching requirement, if applicable, in PDF/UA.
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 include an alternative description. This requirement is embodied by requiring a certain key value to be present in the PDF representing the embedded media clip. 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.
Notes to the Mapping
There are 61 Success Criteria in WCAG 2.0, each presented as a row in the following table. For each Criterion, the table provides the relevant subsection of PDF/UA. For additional reference the table includes the WCAG 2.0 PDF Techniques and W3C's 2008 report on WCAG 2.0 support in ISO 32000-1.
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 and Section 9 is directed at assistive technologies (AT) delivering the reader software's output to the user. The column denoting PDF/UA's conforming Reader requirements is included for informational purposes, and is more readily applicable to WAI's UAAG initiative than to WCAG 2.0.
Differences with WCAG 2.0
Those Success Criteria PDF/UA does not address are marked in the following table with a "++" and that row is shaded. Success Criteria for which WCAG 2.0 differs from PDF/UA are marked with a ">>", these may be eliminated. Highlighted "??" question marks indicate a concern to be addressed. These marks will be improved.
Caution Regarding Versions
The FDIS has been made available to members of the ISO Committee and those of member bodies participating in ISO TC 171 SC2 WG9. While the FDIS ballot (closing June 23, 2012) is open, ISO/FDIS-14289-1 is NOT available from the ISO website. Publication is expected in Q3 of 2012.
Achieving WCAG 2.0 with PDF/UA
| Normative | Advisory | |||
|---|---|---|---|---|
| WCAG 2.0 | ISO 14289-1 (File) | ISO 14289-1 (Reader) | WCAG 2.0 PDF Techniques | W3C "Support Doc" for ISO 32000-1 |
| 1.1.1 Non-text Content. (A) ++ | 7.3 addresses content requiring text alternatives. 7.18.1 paragraph 4 addresses control descriptions. 7.18.6.2 addresses time-based media alternatives. ++ Test, Sensory and CAPTCHA use-cases are addressed via the technical means employed. ++ 7.1 paragraph 1 sentence 2 addresses decoration. |
8.1 | PDF1 PDF4 |
The PDF specification provides ways to include equivalents for images, as detailed in section 14.9.3 of the ISO 32000-1 PDF specification. |
| 1.2.1 Audio-only and Video-only (Prerecorded). (A) ++ | 7.18.6.2 addresses time-based media alternatives. Design-specific. Authors and developers need to consider this provision and ensure conformance. | 8.11.3 | No Accessibility Support impact. Not applicable to PDF format. Applies to media embedded within PDF documents. | |
| 1.2.2 Captions (Prerecorded). (A) ++ | 7.18.6.2 addresses time-based media alternatives. Design-specific. Authors and developers need to consider this provision and ensure conformance. | 8.11.3 | No Accessibility Support impact. Not applicable to PDF format. Applies to media embedded within PDF documents. | |
| 1.2.3 Audio Description or Media Alternative (Prerecorded). (A) ++ | 7.18.6.2 addresses time-based media alternatives. Design-specific. Authors and developers need to consider this provision and ensure conformance. | 8.11.3 | No Accessibility Support impact. Not applicable to PDF format. Applies to media embedded within PDF documents. | |
| 1.2.4 Captions (Live). (AA) ++ | Design-specific. Authors and developers need to consider this provision and ensure conformance. | 8.11.3 prohibits conforming readers from interfering with the captioning provided for content (live and otherwise) accessed through a conforming file. | No Accessibility Support impact. Not applicable to PDF format. Applies to media embedded within PDF documents. | |
| 1.2.5 Audio Description (Prerecorded). (AA) ++ | 7.18.6.2 addresses time-based media alternatives. Design-specific. Authors and developers need to consider this provision and ensure conformance. | 8.11.3 prohibits conforming readers from interfering with extended content accessed through a conforming file. | No Accessibility Support impact. Not applicable to PDF format. Applies to media embedded within PDF documents. | |
| 1.2.6 Sign Language (Prerecorded). (AAA) ++ | Design-specific. Authors and developers need to consider this provision and ensure conformance. | 8.11.3 prohibits conforming readers from interfering with extended content accessed through a conforming file. | No Accessibility Support impact. Not applicable to PDF format. Applies to media embedded within PDF documents. | |
| 1.2.7 Extended Audio Description (Prerecorded). (AAA) ++ | Design-specific. Authors and developers need to consider this provision and ensure conformance. | 8.11.3 prohibits conforming readers from interfering with extended content accessed through a conforming file. | No Accessibility Support impact. Not applicable to PDF format. Applies to media embedded within PDF documents. | |
| 1.2.8 Media Alternative (Prerecorded). (AAA) ++ | 7.18.6.2 addresses time-based media alternatives. Design-specific. Authors and developers need to consider this provision and ensure conformance. | 8.11.3 prohibits conforming readers from interfering with extended content accessed through a conforming file. | No Accessibility Support impact. Not applicable to PDF format. Applies to media embedded within PDF documents. | |
| 1.2.9 Audio-only (Live). (AAA) ++ | Design-specific. Authors and developers need to consider this provision and ensure conformance. | 8.11.3 prohibits conforming readers from interfering with extended content accessed through a conforming file. | No Accessibility Support impact. Not applicable to PDF format. Applies to media embedded within PDF documents. | |
| 1.3.1 Info and Relationships. (Level A) | 7.1 7.2 7.3 7.4 ?>>? * 7.5 7.6 7.7 7.8 7.9 7.10 7.20 7.21 & above address content. 7.17 & 7.18 address annotations. |
8.1 | ?? PDF3 PDF6 PDF9 PDF10 PDF11 PDF12 PDF17 PDF20 PDF21 |
PDF provides a variety of ways to convey information and relationships with semantic elements such as headings, lists, tables, and paragraphs. |
| 1.3.2 Meaningful Sequence. (Level A) | 7.2 paragraph 2 7.17 addresses navigation features. 7.18.3 addresses tab order in annotations. |
8.2 paragraph 1 | PDF3 | PDF supports a defined programmatic order to content. |
| 1.3.3 Sensory Characteristics. (Level A) | 7.1 paragraph 6 and 7. | No Accessibility Support impact. This is design-specific and can be met by avoiding instructions such as "click the red button". | No Accessibility Support impact. This is design-specific and can be met by avoiding instructions such as "click the red button". | |
| 1.4.1 Use of Color. (Level A) | 7.1 paragraph 6. | This is design-specific. Application or document authors need to consider this provision and ensure conformance. | No Accessibility Support impact. This is design-specific. | |
| 1.4.2 Audio Control. (Level A) ++ | Design-specific. Authors and developers need to consider this provision and ensure conformance. | Design-specific. Application or document authors need to consider this provision and ensure conformance. | No Accessibility Support impact. This relates to embedded media players within a PDF document. | |
| 1.4.3 Contrast (Minimum). (Level AA) ++ | Design-specific. Authors and developers need to consider this provision and ensure conformance. | Conformance in PDF requires ISO 14289 conforming files and readers. The manner in which developers support this success criterion in PDF is not defined in ISO 14289 or ISO 32000. | No Accessibility Support impact. This is design-specific. | |
| 1.4.4 Resize text. (Level AA) | Conforming files may be exported to clean HTML for resizing and restyling. | Conformance in PDF requires ISO 14289 conforming files and readers. The manner in which developers support this success criterion in PDF is not defined in ISO 14289 or ISO 32000. | "Adobe Reader provides a zooming feature for text." See General Technique G142. | |
| 1.4.5 Images of Text. (Level AA) | 7.3 paragraph 6 | Not applicable. | PDF7 | No Accessibility Support impact. This is design-specific. |
| 1.4.6 Contrast (Enhanced). (Level AAA) ++ | 7.1 paragraph 6. | Design-specific. Application or document authors need to consider this provision and ensure conformance. | No Accessibility Support impact. This is design-specific. Authors may need to avoid using [contrast to show] regions or carefully check color contrast possibilities for these areas. | |
| 1.4.7 Low or No Background Audio. (Level AAA) ++ | Design-specific. Authors and developers need to consider this provision and ensure conformance. | Design-specific. Application or document authors need to consider this provision and ensure conformance. | No Accessibility Support impact. Background audio can be avoided or a mechanism can be provided to silence it. | |
| 1.4.8 Visual Presentation. (Level AAA) ++ | Design-specific. Authors and developers need to consider this provision and ensure conformance. | While ISO 14289 does not address this success criterion, conformance in PDF requires ISO 14289 conforming files and readers. The manner in which developers support this success criterion in PDF is not defined in ISO 14289 or ISO 32000. | Application or document authors need to consider this provision and ensure conformance. | |
| 1.4.9 Images of Text (No Exception). (Level AAA) | 7.3 paragraphs 1 and 3. | Not applicable. | PDF7 | No Accessibility Support impact. This is design-specific. |
| 2.1.1 Keyboard. (Level A) | 7.19, paragraph 3. ?>>? | 8.1 paragraph 2, bullet 3. Conformance in PDF requires ISO 14289 conforming files and readers. The manner in which developers support this success criterion in PDF is not defined in ISO 14289 or ISO 32000. | ??PDF3 ??PDF11 PDF23 |
PDF forms and other interactive elements are operable through a keyboard interface without requiring specific timing. |
| 2.1.2 No Keyboard Trap. (Level A) ++ | Design-specific. Developers need to consider this provision and ensure conformance. | 8.7. The manner in which developers support this success criterion in PDF is not defined in ISO 14289 or ISO 32000. | Authors who design PDF forms and utilize scripting need to test to ensure that keyboard traps are not created when moving from control to control. | |
| 2.1.3 Keyboard (No Exception). (Level AAA) ++ | 7.19, paragraph 3. | 8.1 paragraph 2, bullet 3. Conformance in PDF requires ISO 14289 conforming files and readers. The manner in which developers support this success criterion in PDF is not defined in ISO 14289 or ISO 32000. | PDF forms do not require specific timing for keyboard access to standard controls. | |
| 2.2.1 Timing Adjustable. (Level A) ++ | 7.19, paragraph 3. | 8.11.3 paragraphs 2 and 3. | No Accessibility Support impact. This is design-specific. | |
| 2.2.2 Pause, Stop, Hide. (Level A) ++ | 7.19 | 8.7 | No Accessibility Support impact. This is design-specific. | |
| 2.2.3 No Timing. (Level AAA) ++ | 7.19 | 8.7 | No Accessibility Support impact. This is design-specific. | |
| 2.2.4 Interruptions. (Level AAA) ++ | 7.19 | 8.7 | No Accessibility Support impact. This is design-specific. | |
| 2.2.5 Re-authenticating. (Level AAA) ++ | 7.19 | Design-specific. Developers need to consider this provision and ensure conformance. | No Accessibility Support impact. This is design-specific. | |
| 2.3.1 Three Flashes or Below Threshold. (Level A) ++ | 7.1, paragraph 5 | Design-specific. Developers need to consider this provision and ensure conformance. | No Accessibility Support impact. This is an author consideration for embedded media in PDF. | |
| 2.3.2 Three Flashes.(Level AAA) ++ | 7.1, paragraph 5 | Design-specific. Developers need to consider this provision and ensure conformance. | No Accessibility Support impact. This is design-specific. | |
| 2.4.1 Bypass Blocks. (Level A) | 7.8 7.1 paragraphs 1 and 2 |
8.9 | ??PDF9 PDF4 |
PDF allows documents to be tagged with headings which can be used in conjunction with assistive technologies to bypass sections of content. |
| 2.4.2 Page Titled. (Level A) | 7.1 paragraphs 8 and 9 | 8.8 | PDF18 | PDF allows documents to be titled. |
| 2.4.3 Focus Order. (Level A) | 7.1, paragraph 2 7.2 paragraph 1 7.18.1, paragraph 2 7.18.3 |
8.1, 8.9 | PDF3 ?? PDF9 |
PDF provides the ability for authors to control the tab and reading order. |
| 2.4.4 Link Purpose (In Context). (Level A) ++ | 7.18.1 paragraph 2 7.18.5 |
8.1 | PDF11 PDF13 |
No Accessibility Support impact. This is design-specific. |
| 2.4.5 Multiple Ways. (Level AA) | 7.17 7.18.5 |
8.9 | PDF2 | No Accessibility Support impact. This is design-specific. |
| 2.4.6 Headings and Labels. (Level AA) | 7.4 | 8.9 | No Accessibility Support impact. This is design-specific. | |
| 2.4.7 Focus Visible. (Level AA) | Not applicable. | 8.7, 8.9 | "Adobe Reader provides information about page numbering" | |
| 2.4.8 Location. (Level AAA) | Not applicable, HTML-specific. | Design-specific. Developers need to consider this provision and ensure conformance. | ??PDF14 ??PDF17 |
No Accessibility Support impact. This is design-specific. |
| 2.4.9 Link Purpose (Link Only). (Level AAA) | 7.18.5 paragraph 2 | 8.10.1 | PDF11 PDF13 |
No Accessibility Support impact. This is design-specific. |
| 2.4.10 Section Headings. (Level AAA) | 7.4 | 8.9, bullet 2 | PDF provides support for headings to convey content organization. | |
| 3.1.1 Language of Page. (Level A) | 7.2, paragraph 3 | 8.2, paragraph 3 | PDF16 PDF19 |
PDF provides support for language identification for documents. |
| 3.1.2 Language of Parts. (Level AA) | 7.2, paragraph 3 | 8.2, paragraphs 2 and 3 | PDF19 | PDF provides support for language identification for parts of documents. |
| 3.1.3 Unusual Words. (Level AAA) ++ | Not specifically addressed. See IS0 32000-1 14.9.5. | Developers wishing to support this success criteria must support the "E" property in Marked Content. See ISO 32000-1, 14.9.5. | No Accessibility Support impact. PDF document authors can provide a link to a definition of unusual words or phrases. | |
| 3.1.4 Abbreviations. (Level AAA) ++ | Not specifically addressed. See IS0 32000-1 14.9.5. | Developers wishing to support this success criteria must support the "E" property in Marked Content. See ISO 32000-1, 14.9.5. | PDF8 | PDF supports abbreviations in tagged PDF by using a span and an abbreviation property. |
| 3.1.5 Reading Level. (Level AAA) ++ | Authors may provide conforming content | Not applicable | No Accessibility Support impact. This is design-specific. | |
| 3.1.6 Pronunciation. (Level AAA) ++ | Authors may include conforming content. | Design-specific. Developers need to consider this provision and ensure conformance. | PDF documents support this success criterion when document authors provide pronunciation information using general techniques G120, G121, G62. | |
| 3.2.1 On Focus. (Level A) ++ | 7.18.1, paragraph 2, 7.19 paragraph 2 ** |
8.7 | Standard controls in PDF do not initiate changes of context when changing settings. | |
| 3.2.2 On Input. (Level A) ++ | 7.18.1, paragraph 2, 7.19 paragraph 2 ** |
8.7 | PDF15 | No Accessibility Support impact. This is design-specific. |
| 3.2.3 Consistent Navigation. (Level AA) | Not applicable - HTML specific. | Not applicable. | ??PDF14 ??PDF17 |
No Accessibility Support impact. This is design-specific. |
| 3.2.4 Consistent Identification. (Level AA) ++ | Design-specific. Developers need to consider this provision and ensure conformance. | Not applicable | No Accessibility Support impact. This is design-specific. | |
| 3.2.5 Change on Request. (Level AAA) | 7.19, paragraph 2 | 8.7 | Changes of context are not initiated by default for any user interface controls. | |
| 3.3.1 Error Identification. (Level A) ++ | 7.19 Design-specific. Authors need to consider this provision and ensure conformance. | 8.7 Design-specific. Developers need to consider this provision and ensure conformance. | PDF5 PDF22 |
PDF form controls that accept user input provide validation functionality which can alert the user of the error in text. |
| 3.3.2 Labels or Instructions. (Level A) | 7.18.1 7.18.4 |
8.10.2 | PDF5 PDF10 |
PDF form controls allow authors to provide labels or instructions. |
| 3.3.3 Error Suggestion (Level AA) ++ | Design-specific. Authors and developers need to consider this provision and ensure conformance. | 8.10.2 | PDF5 PDF22 |
PDF supports scripting functionality which allows customization of error responses. |
| 3.3.4 Error Prevention (Level AA) ++ | Design-specific. Authors and developers need to consider this provision and ensure conformance. | 8.10.2 | No Accessibility Support impact. This is design-specific. PDF authors may utilize validation or server-side error-checking prior to final submission. | |
| 3.3.5 Help: Context-sensitive help is available. (Level AAA) ++ | Design-specific. Authors and developers need to consider this provision and ensure conformance. | Design-specific. Developers need to consider this provision and ensure conformance. | PDF authors can provide context-sensitive help by utilizing the following general techniques: G71, G184. | |
| 3.3.6 Error Prevention (Level AAA) ++ | Design-specific. Authors and developers need to consider this provision and ensure conformance. | Design-specific. Developers need to consider this provision and ensure conformance. | No Accessibility Support impact. This is design-specific. PDF authors may utilize validation or server-side error-checking prior to final submission. | |
| 4.1.1 Parsing (Level A) | In PDF, applies to dynamic XFA-PDF only, not applicable in PDF/UA. | Not Applicable | PDF documents are not implemented using markup languages. | |
| 4.1.2 Name, Role, Value (Level A) | 7.18 | 8.10 | PDF10 PDF11 |
Standard controls in PDF provide name, role, and value when used according to specification. |
Footnotes
* - PDF/UA requires logical heading levels for conformance. UNDER DISCUSSION: The non-normative "explanatory" text notwithstanding, WCAG 2.0 Success Criterion 1.3.1 appears to require that if headings are used as a navigational feature of the document then they must represent the document content's "structure and relationships". WCAG experts differ on this.
** - WCAG 2.0 conformance applies to Actions other than scripts which may trigger a change of context onFocus. Objects in PDF have inherent properties, Actions are part of these properties, and Actions are therefore perceivable via conforming viewers and AT, but PDF/UA does not specify sequence in Action announcements.
Implementers of conforming PDF readers should consider that conformance with WCAG 2.0 SC 3.2.1 and SC 3.2.2 requires reporting of the onFocus Action or scripted event to the user only prior to the event.
References
Web Content Accessibility Guidelines (WCAG) 2.0, W3C Recommendation 11 December 2008
ISO 14289-1, Document management applications -- Electronic document file format enhancement for accessibility -- Part 1: Use of ISO 32000-1 (PDF/UA)
ISO 32000-1:2008, Document management -- Portable document format -- Part 1: PDF 1.7
Accessibility Support Documentation for PDF, 2008 W3C Report
PDF Techniques for WCAG 2.0, W3C Techniques for WCAG 2.0
