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A primer on PDF accessibility

The primary goal of accessibility compliance is to ensure that individuals with disabilities can access and use information equally. This is achieved through measures that either directly assist the user or support the assistive technologies they use.

Why accessibility matters for humans and machines​

A truly accessible PDF serves:

  • Users: An accessible PDF provides navigational aids like a clear structure, bookmarks, and proper reading order. The accessible PDF makes content legible through suitable contrast and colors and provides text alternatives for non-text content like images for screen readers. This helps not only users with permanent visual impairments but also those with temporary disabilities or anyone trying to read a document on a small mobile screen.
  • Machines: A well-tagged PDF becomes a machine-readable document, enabling robust data extraction, reliable text searching, and content re-use, where you can rearrange content to fit different screen sizes without losing its meaning or structure.

Pillars of an accessible PDF​

Key components determine a PDF document’s accessibility:

  • Searchable and selectable text: The document must contain real text, not just images of text, so screen readers can access it and users can search it.
  • Alternative text for images: All meaningful images must have alternative text (alt-text) that describes their content or function.
  • Logical structure and reading order: You must tag the document with a hierarchical structure tree that defines the reading order and identifies elements like headings, paragraphs, lists, and tables.
  • Navigational aids: Bookmarks, a table of contents, and logical heading structures help users navigate the document efficiently.
  • Contrast and visual design: To improve readability, text must have enough contrast against its background. However, contrast should not be the only means of conveying information.
  • Language specification: To allow screen readers to use the correct pronunciation, specify the primary language and any language changes.

The following standards and best practices define these accessibility requirements:

Human in the loop​

While this SDK handles the technical implementation, creating accessible PDF documents requires human understanding and judgment. Accessibility goes beyond technical compliance. Accessibility requires understanding how people actually use documents.

  • Expertise: Understanding the standards, formats, and workflows.
  • Perspective: Thinking from the user’s point of view.
  • Tools: Using software that handles the technical heavy lifting.
  • Plain language: Writing content that people with cognitive disabilities can understand.

The accessibility software provided by Pdftools ensures technical compliance, but human oversight is essential to confirm that the document is genuinely usable and understandable. This includes using clear, simple language and avoiding jargon—principles of plain language that make documents accessible to people with cognitive disabilities, learning differences, or limited literacy skills.

Accessibility guides​

Learn how to improve PDF accessibility using the Toolbox add-on SDK by following these guides: