PDF accessibility means making a PDF document readable and usable by people who use assistive technology, primarily screen readers, but also by people with low vision who zoom into content, and by anyone who needs to navigate or search a long document efficiently. An accessible PDF is not just a nicety; for public-sector organisations and many commercial publishers, it is a legal requirement under the Equality Act 2010 and the Public Sector Bodies Accessibility Regulations 2018.
What makes a PDF accessible
An accessible PDF has several characteristics that most quickly-created documents lack.
Tagged structure is the foundation of accessibility. PDF tags define the logical reading order of the content, what is a heading, what is a paragraph, what is a list item, what is a figure. Screen readers use these tags to navigate the document in a meaningful sequence rather than just reading content in the order it appears on the page (which can be confusing in multi-column layouts, tables, and documents with sidebars).
Alternative text for images allows screen readers to describe images, charts, and diagrams to users who cannot see them. An image with no alt text is simply skipped. A decorative image should be marked as such so it is not announced. An informational image or chart needs a meaningful description.
Selectable text means the PDF contains actual text data rather than images of text. A scanned PDF without OCR contains no selectable text and is almost entirely inaccessible to screen readers. Text from a digital source, a Word document, a designed layout tool, is searchable and selectable by default.
Document language needs to be specified so screen readers use the correct pronunciation and reading rules. A PDF in English that is not tagged with the language may be read using incorrect phonetic rules, making it difficult to understand.
Meaningful link text matters for navigation. A link that says "click here" conveys nothing to a screen reader user who is navigating by listing all the links on a page. Link text should describe the destination: "Download the annual report PDF" or "Visit the HMRC Self Assessment portal."
Scanned PDFs and accessibility
A scanned PDF is essentially a photograph of a document. Without OCR (optical character recognition), it has no text data and no structure. Screen readers cannot read it at all.
Running OCR on a scanned document is the minimum step to make it usable. OCR converts the image content to text, making it selectable and searchable. However, even after OCR, a scanned document is not fully tagged, the reading order may be unreliable, images within the scan will not have alt text, and the structural hierarchy (headings, paragraphs, lists) will not be defined.
For a scanned document that needs to meet accessibility standards, OCR is the starting point, not the end. Proper tagging and remediation in a tool like Adobe Acrobat Pro is then required to create a genuinely accessible output.
Creating accessible PDFs at source
The most efficient way to produce an accessible PDF is to build accessibility into the document before exporting to PDF. Word, Google Docs, InDesign, and most professional document creation tools support accessibility features at the source level.
In Microsoft Word:
- Use built-in heading styles (Heading 1, Heading 2, etc.) rather than manually increasing font size to indicate sections.
- Add alt text to images via right-click → Edit Alt Text.
- Use the Accessibility Checker (Review → Check Accessibility) to identify and fix issues before exporting.
- When exporting to PDF, ensure "Document structure tags for accessibility" is checked in the export options.
In Google Docs, accessibility is less complete at export. Heading structure carries through to the PDF, but alt text for images and some more complex structural elements may require remediation in a PDF tool after export.
Testing accessibility
After producing a PDF, test it before distributing. Adobe Acrobat's full version includes an accessibility checker under Tools → Accessibility → Full Check. It flags missing tags, missing alt text, reading order problems, and missing document language.
For a free alternative, the PAC (PDF Accessibility Checker) tool from the Swiss PDF accessibility foundation is widely used by accessibility professionals. It checks against the PDF/UA standard, which is the international standard for accessible PDFs.
For a basic manual check, try navigating the document with a screen reader such as NVDA (free, Windows) or VoiceOver (built into macOS and iOS). This gives you a real sense of the experience for a visually impaired user, including whether reading order makes sense, whether images are described, and whether the structural hierarchy is meaningful.
Common accessibility problems and how to fix them
No tags, export from the source document with tags enabled, or use Adobe Acrobat Pro to auto-tag and then manually correct.
Incorrect reading order, open the Tags panel in Acrobat and verify the order matches the intended reading sequence. Multi-column layouts and documents with sidebars often need manual correction.
Missing alt text, add descriptions in the source document before exporting, or use Acrobat's TouchUp Properties to add alt text to images after the fact.
Scanned images of text, run OCR in Acrobat (Tools → Scan and OCR) to convert image-based text to actual text data, then review for accuracy.
Low colour contrast, this is a design issue that must be fixed in the source document. Light grey text on white background, for example, fails WCAG contrast requirements and is hard to read even for users without visual impairments.