An accessible PDF is one that can be used by everyone — including people who are blind or have low vision, people who use screen readers, and people with cognitive or motor disabilities. Most PDFs distributed professionally fail accessibility requirements without their creators realizing it. The gap between a visually presentable PDF and an accessible one involves specific technical features that don't add themselves automatically.
Why It Matters Beyond Legal Compliance
In many countries, organizations that produce public-facing documents are legally required to make them accessible. The Americans with Disabilities Act in the US, the European Accessibility Act, and equivalent legislation elsewhere create enforceable requirements for accessible digital content. Government agencies, educational institutions, and many businesses operate under these rules.
Beyond compliance, accessible PDFs are simply more useful. A well-structured accessible document is easier to navigate for everyone — not just screen reader users. Clear headings, logical reading order, and descriptive alt text improve the experience for all readers, including people on mobile devices, people in a hurry, and people whose first language isn't the document's language.
Tags: The Foundation of PDF Accessibility
An accessible PDF is a tagged PDF. Tags are a hidden structural layer that describes what each element of the document is — this is a heading, this is a paragraph, this is a list item, this is an image with this description. Screen readers use tags to navigate and announce content correctly. Without tags, a screen reader reads the document as an undifferentiated stream of text, or can't read it at all.
Tags are added automatically when you export a PDF from Word using File > Save As > PDF with the "Document structure tags for accessibility" option enabled. This is the fastest way to get basic tagging without manual work. For more complex documents — multi-column layouts, tables, documents with many images — the automatic tagging often needs manual review and correction in Adobe Acrobat Pro.
Reading Order: What Screen Readers Follow
A screen reader reads content in the document's tag order — not the visual order on the page. For a simple single-column document, these are usually the same. For complex layouts with sidebars, callout boxes, multi-column text, and floating images, the tag order can differ significantly from the visual reading order.
In Adobe Acrobat Pro, the Reading Order tool (Tools > Accessibility > Reading Order) lets you see and correct the order in which a screen reader will process content. A document that looks well-organized visually may have a completely illogical reading order for someone using assistive technology. Checking and fixing this is an essential step for truly accessible documents.
Alt Text for Images
Every image in an accessible PDF needs alternative text — a written description that a screen reader announces in place of the image. A chart showing quarterly sales needs alt text describing what the chart shows: "Bar chart showing Q1-Q4 revenue. Q4 is highest at $2.4M." A decorative divider line or background texture should be marked as an artifact so the screen reader skips it rather than announcing it as an image.
Alt text can be added in Word before export (right-click an image > Edit Alt Text) or in Acrobat Pro after the fact (right-click an image in the Tags panel > Properties > Alt Text). Adding alt text in Word before export is more efficient for documents with many images.
Heading Structure and Navigation
Screen reader users navigate long documents by jumping between headings — the way sighted readers scan headings to find sections. For this to work, headings must be tagged as headings (H1, H2, H3) rather than just styled as large, bold text.
In Word, using proper Heading styles (not manual bold and font-size formatting) creates the heading structure that carries over into the PDF as tagged headings. This is one of the clearest arguments for using Word's built-in styles rather than manual formatting throughout a document — the structure serves both accessibility and the visual design simultaneously.
Color and Contrast
Accessibility isn't only about screen readers. People with low vision or color blindness may be able to read a document visually but struggle with insufficient contrast or color-dependent information. The Web Content Accessibility Guidelines (WCAG) standard, which is widely used for PDF accessibility as well, requires a minimum contrast ratio of 4.5:1 between text and background for normal text.
A practical check: if information is conveyed only through color — "items in red require attention" — add a secondary indicator (a symbol, bold text, or a label) so the information is accessible to someone who can't distinguish the color. Never rely on color alone to communicate meaning.
Checking a PDF's Accessibility
Adobe Acrobat Pro includes an Accessibility Checker (Tools > Accessibility > Full Check) that scans the document against the PDF/UA standard and lists specific issues with their locations. It catches missing alt text, incorrect reading order, missing document language declaration, and other common problems.
PAC (PDF Accessibility Checker) is a free tool that provides thorough accessibility checking against PDF/UA standards. For organizations producing accessible PDFs regularly, running every document through PAC before distribution is a good practice. The checker gives you a clear list of what needs fixing rather than a general pass/fail result.
The Special Problem of Scanned PDFs
A Scanned PDF with no text layer is completely inaccessible — there is no text for a screen reader to announce, no structure to navigate, nothing. OCR converts the image to text, which is the minimum required to make a scanned document usable. But OCR alone doesn't add proper tags, reading order, or alt text — it just creates a text layer. Full accessibility from a scanned document requires OCR plus the tagging and structure work described above.