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PDF/UA vs. WCAG: How the two standards fit together
Anyone who has to publish accessible PDFs runs into two sets of rules: PDF/UA and WCAG. They do not compete, they complement each other. This guide explains what each standard covers and why you need both in practice.
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PDF/UA: the technical standard for the file format
PDF/UA (“Universal Accessibility”) is standardised as ISO 14289. PDF/UA-1 (ISO 14289-1:2014) is based on PDF 1.7 and is today’s widely used reference; PDF/UA-2 (ISO 14289-2:2024) carries the requirements over to PDF 2.0. PDF/UA defines how a PDF must be built internally so that assistive technologies can process it reliably.
Typical PDF/UA requirements include:
- All meaningful content is tagged, and decorative elements are marked as artifacts.
- Tags are used with the correct semantics, such as
H1toH6for headings orTable,TR,THandTDfor tables. - The document has a title that is displayed (
DisplayDocTitle), a default language (/Lang) and a PDF/UA identifier in its XMP metadata. - All fonts are embedded and map unambiguously to Unicode.
- Annotations such as links are part of the structure.
The test criteria are collected in the Matterhorn Protocol published by the PDF Association. Some of them can be checked automatically, for example with PAC or veraPDF; the rest requires human judgement.
WCAG: guidelines for accessible content
The W3C’s Web Content Accessibility Guidelines (WCAG) are written to be technology-neutral. WCAG 2.1 and WCAG 2.2 are the current versions, and most legal requirements ask for conformance level AA. WCAG does not describe a file format but success criteria for content: Is the text contrast sufficient? Do images have a text alternative? Are links understandable? Is the order meaningful?
For PDFs, the W3C has published dedicated sufficient techniques, PDF1 through PDF23. They show how individual success criteria can be met in PDF, for example alternative text for figures, table headers or specifying the document language.
EN 301 549: the bridge between the two
In the EU, the harmonised standard EN 301 549 is the key reference. Clause 9 covers web content, and clause 10 covers non-web documents, which include PDFs. Clause 10 applies the WCAG success criteria to documents almost one-to-one. PDFs offered by public bodies under the Web Accessibility Directive, or by businesses under the European Accessibility Act, are usually measured against these criteria.
EN 301 549 does not make PDF/UA mandatory, but in practice PDF/UA is the proven way to meet the WCAG requirements for PDFs on a sound technical basis.
Comparison at a glance
| Aspect | PDF/UA | WCAG |
|---|---|---|
| Publisher | ISO (standard 14289) | W3C |
| Scope | PDF files only | Web content, and documents via EN 301 549 |
| Focus | Technical structure: tags, metadata, fonts | Perceivable, operable, understandable, robust |
| Conformance levels | None, all requirements apply | A, AA, AAA |
| Test catalogue | Matterhorn Protocol | Success criteria and techniques PDF1–PDF23 |
| Colour contrast | Not covered | Criterion 1.4.3 (at least 4.5:1 at level AA) |
What WCAG requires but PDF/UA does not
A PDF can formally conform to PDF/UA and still fail WCAG criteria. Examples:
- Contrast (1.4.3): light grey text on a white background is not a PDF/UA error, but it is a WCAG failure.
- Use of colour (1.4.1): information must not be conveyed by colour alone, for example in charts.
- Link purpose (2.4.4): “click here” may be tagged correctly but is meaningless without context.
- Quality of alternative text (1.1.1): PDF/UA requires alternative text to exist; WCAG requires it to convey the purpose of the image.
What PDF/UA requires in more detail than WCAG
Conversely, PDF/UA is stricter and more precise on technical matters. It requires embedded fonts, a PDF/UA identifier in the metadata, content that is either tagged or marked as an artifact, and a tab order that follows the structure on pages with annotations (/Tabs /S). WCAG addresses such points only indirectly, through criterion 4.1.2 (name, role, value) or through the techniques.
Recommendation for practice
- Make documents accessible at the source, for example with styles in Word or InDesign, and export them as tagged PDFs.
- Check the PDF technically: with the EasyPDFUA PDF/UA check, PAC or veraPDF.
- If basics such as title, language or baseline tags are missing, tag the PDF retroactively.
- Review the content-related WCAG criteria manually: contrast, alternative text, headings, link text and reading order.
Frequently asked questions
Is PDF/UA conformance enough for WCAG?
Not automatically. PDF/UA covers the technical structure but does not check colour contrast or the clarity of link text, for example. WCAG conformance also requires a content review.
Which WCAG version applies to PDFs?
EN 301 549 version 3.2.1 references WCAG 2.1 level AA. Many organisations already follow WCAG 2.2, which adds a few criteria.
Should I use PDF/UA-1 or PDF/UA-2?
PDF/UA-1 currently has the broadest support in checkers, screen readers and authoring tools. PDF/UA-2 requires PDF 2.0 and is being adopted by software gradually.
Can EasyPDFUA check WCAG criteria?
EasyPDFUA examines the technical PDF structure, such as tags, title, language, fonts and links. Content-related WCAG criteria such as contrast or the quality of alternative text have to be checked manually.