Creating accessible PDF documents (Part 2/3)
What does an accessible PDF look like?
After our general introduction (part 1/3), this second part shows what an accessible PDF document should look like in practice.
A PDF should always be easy to read. Use a suitable layout and sufficient contrast so visually impaired people can access all information.
Accessibility in this context can also affect many groups, for example people with limited literacy, reading difficulties, or non-native speakers. In this article, however, we focus on documents that can be used by blind and visually impaired users. That means the PDF must be structured so screen readers can process it correctly.
Quick overview: key features of an accessible PDF
- Use tags, meaning a tagged or structured PDF.
- Prepare accessibility early by using styles, and by planning layout and text flow.
- Add bookmarks, links, and tags. Also check security settings and speech output behavior. Define metadata such as document title and initial view.
- Optimize for text reflow, contrast mode, reading order, alternative text for images, data tables, headings, paragraphs, lists, links, and bookmarks.
- Tab order, language settings, and character encoding also matter.
Why are tags important?
Tags are essential for screen reader users because they provide the document structure needed to navigate and understand content. Users need to identify headings, paragraphs, lists, graphics, and data tables quickly and reliably.
Structural elements such as reading order, bookmarks, and footnotes are also relevant. They control how content is presented by assistive technology and help preserve structure during format conversions and zoom/reflow scenarios.
But tags alone are not enough. Accessibility is broader and requires a complete approach. This is covered in part 3.
In summary, accessible PDFs require tags, headings, and consistent styles. Documents should avoid image-only content, or provide proper alternative text. Bookmarks improve navigation. Screen reader access must not be blocked by security settings.
Universal Accessibility: PDF/UA
PDF offers variants such as PDF/A and PDF/X for archiving and print use cases. For accessibility, the key standard is PDF/UA. UA stands for Universal Accessibility.
PDF/UA is designed specifically for accessible documents. It is especially relevant for developers of tools that create, read, process, and validate PDFs, and for providers of assistive technologies. PDF/UA is the industry standard, while EN 301549 is the legally relevant European standard in this context.
For truly accessible PDFs, additional requirements must be considered, especially WCAG guidelines and core usability principles. Anyone creating tagged PDFs should therefore understand PDF/UA, EN 301549, and national regulations such as BITV.
Checking PDFs for accessibility
Use the PAC test (PDF Accessibility Checker) to verify whether a PDF meets key testable PDF/UA requirements. A successful PAC test is a good indicator, but WCAG requirements should also be considered.
Summary: most important requirements for accessible PDFs
- Use the right software: for example Adobe Acrobat DC, Adobe InDesign, or Microsoft Word.
- Follow layout rules early: design, structure, and language should be planned before export.
- Validate for accessibility after creation. Consider WCAG, BITV, ISO 14289-1, EN 301549, and the Matterhorn Protocol.