Toolbelt

PDFs offer the basic accessibility functions like bookmarks for navigation, structured content for navigation, content reading order, page numbering, and image alternative text inclusion. However, the fixed layout of PDF is restrictive. The print-centric nature of PDF limits content interaction to zoom and scroll, hampering low vision or neurodiverse users reading the content. The underlying document structure also lacks any form of semantic identification to help screen reading software identify the structure or purpose of content or hyperlinks. This makes it easier to "get lost" in a PDF document when using screen reading software.

Conversely, the EPUB format offers basic accessibility functions like bookmarks for navigation, structured content for navigation, content reading order, page numbering, and image alt text inclusion. With their dynamic layout, EPUBs can easily incorporate long descriptions and video/audio transcripts where they are needed, simplifying navigation. The dynamic layout allows users to adjust the font family, font size, and font contrast ratios on the text, greatly aiding low vision or neurodiverse users.

The main advantage of EPUB over PDF is that it uses structured markup of titles, headings, links, notes, tables, and more, which allows digital text to speech and screen reading software to function effectively.  EPUB files also provide an optimal experience for users across all devices, as text size and page layouts are adjustable. This allows users to personalize their reading experience to suit their preferences. EPUB files allow linked navigation, multimedia content, and videos too.  EPUB files are up to 90% smaller than PDF files meaning faster download times and more efficient data usage for mobile users.