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WCAG 2.1 AA requirements for PDFs, explained
Short answer: For a PDF, WCAG 2.1 Level AA mainly means: the file is tagged so its structure (headings, lists, tables) is available to assistive technology; content is read in a logical order; images have text alternatives; the document has a title and language set; text has enough color contrast; links make sense; and form fields have labels. Software can test many of these, but not all.
The criteria that matter most for PDFs
| WCAG 2.1 criterion | What it means for a PDF | Can software check it? |
|---|---|---|
| 1.1.1 Non-text Content | Every meaningful image has alternative text; decorative images are marked as artifacts | Partly: whether alt text exists, not whether it is accurate |
| 1.3.1 Info and Relationships | Headings, lists, tables and their headers are tagged | Partly: tags exist; whether they match the visual structure needs a person |
| 1.3.2 Meaningful Sequence | The tag order matches the logical reading order | No, needs a person |
| 1.4.3 Contrast (Minimum) | Text has a contrast ratio of at least 4.5:1 (3:1 for large text) | Partly, with specialized tools |
| 1.4.5 Images of Text | Text is real text, not a picture of text (scans need OCR) | Partly |
| 2.4.2 Page Titled | The document has a title that is shown in the title bar | Yes |
| 2.4.4 Link Purpose (In Context) | Link text or its context says where the link goes | Partly |
| 3.1.1 Language of Page | The document language is set | Yes |
| 3.1.2 Language of Parts | Passages in another language are marked | Partly |
| 4.1.2 Name, Role, Value | Form fields have names and roles | Partly |
| 3.3.2 Labels or Instructions | Form fields have visible labels | No, needs a person |
How much software can verify
The Matterhorn Protocol, published by the PDF Association, lists 136 ways a PDF can fail PDF/UA, in 31 checkpoints. 87 of these can be determined by software; the rest need human judgment. Validators such as veraPDF and PAC test the machine-checkable ones.
That is why a passing automated check is necessary but not sufficient. After any remediation, automated or manual, someone should:
- Navigate by headings with a screen reader (H key in NVDA or JAWS) and confirm they reflect the document.
- Read the image descriptions and check they convey the point of each image.
- Read a table cell by cell and confirm headers are announced.
- Read the document start to finish once to confirm the order makes sense.
Make new documents accessible at the source
It is far cheaper to create an accessible PDF than to fix one. In Word: use built-in heading styles, add alt text to images, use real tables with a header row, run Review › Check Accessibility, then save as PDF with “Document structure tags for accessibility” enabled.
Frequently asked questions
- Is PDF/UA the same as WCAG?
- No. PDF/UA (ISO 14289) is the technical standard for accessible PDF files. WCAG is the standard the ADA Title II rule requires. A PDF that conforms to PDF/UA meets most WCAG requirements that relate to file structure; WCAG also covers things like contrast and meaningful link text.
- Does a PDF need to be tagged?
- In practice, yes. Tags are how a PDF exposes headings, lists, tables and reading order to screen readers, which several WCAG criteria require.