EPUB and PDF are the two dominant formats for digital book distribution. EPUB is a reflowable, reader-controlled format designed for reading on screens. PDF is a fixed-layout format that preserves the exact appearance of the printed page. Understanding the difference determines which format is right for your book — and in most cases, you will need both.
What Is EPUB?
EPUB (Electronic Publication) is the international standard format for digital books, maintained by the W3C (World Wide Web Consortium). An EPUB file is essentially a structured web document packaged inside a container — the text is coded in HTML and CSS, images are embedded, and the whole thing is compressed into a single .epub file.
The defining characteristic of EPUB is reflowability: the text repositions itself to fit whatever screen size, font size, or reading environment the reader uses. Increase the font size, and the text reflows. Switch to a narrower screen, and the layout adjusts. The reader is in control of their reading experience.
What Is PDF?
PDF (Portable Document Format) is a fixed-layout format developed by Adobe. A PDF is a precise digital representation of a printed page — every element is anchored at an exact position. The layout does not change regardless of the screen size or settings the reader uses.
PDFs render identically on every device and in every reader application. This is ideal when the visual layout is critical — tables, multi-column designs, diagrams with precise spatial relationships. It is a significant disadvantage on small screens, where readers are forced to pinch-zoom to read text that does not reflow.
EPUB vs PDF: Side-by-Side Comparison
| EPUB | ||
|---|---|---|
| Layout | Reflowable (reader-controlled) | Fixed (pixel-perfect) |
| Screen adaptability | Excellent | Poor on small screens |
| Font size control | ✅ Reader adjusts | ❌ Fixed |
| Accessibility | ✅ Full WCAG compliance possible | ⚠️ Possible via PDF/UA but harder |
| Platform support | Kindle (via KFX), Apple Books, Kobo, Google Play Books | Widely opened but not ideal for eReaders |
| Bookmarks/navigation | ✅ Built-in chapter navigation | ✅ Via bookmarks |
| Print-accurate layout | ❌ | ✅ |
| Complex layouts (tables, math) | ⚠️ Possible but complex | ✅ |
| File size | Smaller | Larger (especially with images) |
| Editing after export | Difficult | Very difficult |
| Industry standard for ebooks | ✅ Yes | ❌ Not preferred |
When to Use EPUB
EPUB is the right format for:
- Trade books — fiction, narrative non-fiction, biography, memoir. The reading experience on Kindle and Apple Books is what matters, and EPUB delivers it.
- eBook retail distribution — every major retailer (Amazon, Apple Books, Kobo, Google Play Books, Barnes & Noble) accepts EPUB. Amazon converts it to their KFX format internally.
- Accessibility compliance — EPUB Accessibility 1.1 is the standard required by the European Accessibility Act and DAISY certification. PDF/UA is the equivalent for PDFs but is harder to achieve.
- Library and institutional distribution — EPUB is the format required by OverDrive, ProQuest Ebook Central, and EBSCO eBooks.
- Long-form text content — any book where the reader will read continuously rather than reference specific pages.
When to Use PDF
PDF is the right format for:
- Interior print files — your print-ready PDF sent to KDP, IngramSpark, or a commercial printer
- Reference books, textbooks, and technical manuals — where readers navigate non-linearly, and the exact page layout matters
- Illustrated books — where image placement relative to text is critical (art books, photography books, cookbooks)
- Academic papers and journals — PDFs remain the standard for journal article distribution
- Direct downloads from your website — PDFs are universal and require no dedicated reader application
- Regulatory submissions — many accessibility reports, compliance submissions, and institutional documents are required in PDF
Fixed Layout EPUB: A Third Option
Fixed Layout EPUB (FXL EPUB) combines the distribution advantages of EPUB with the visual precision of PDF. It is used for:
- Children's picture books — where illustration and text placement is integral to the design
- Comics and graphic novels
- Highly designed non-fiction — where the visual layout is central to the reading experience (cookbooks, travel books)
- Interactive textbooks
Fixed Layout EPUBs display correctly on Apple Books and Kindle (as KF8), but they have the same small-screen limitations as PDFs and do not reflow.
Which Platforms Accept Which Formats?
| Platform | EPUB | Notes | |
|---|---|---|---|
| Amazon KDP | ✅ (preferred) | ❌ (poor experience) | Amazon converts EPUB to KFX internally |
| Apple Books | ✅ | ❌ | EPUB 3 or Fixed Layout EPUB |
| Kobo | ✅ | ❌ | EPUB 2 or 3 |
| Google Play Books | ✅ | ⚠️ Limited | EPUB preferred |
| Barnes & Noble Nook | ✅ | ❌ | EPUB only |
| IngramSpark (eBook) | ✅ | ❌ | EPUB only |
| OverDrive (library) | ✅ | ❌ | EPUB 3 required for EPUB Accessibility |
| Direct website download | ✅ or PDF | ✅ | Both work |
| JSTOR / academic databases | ❌ | ✅ | PDF standard |
Do You Need Both Formats?
For most books: yes.
A professional publishing workflow typically produces:
- Print-ready PDF — for KDP Print, IngramSpark print, commercial printing
- EPUB 3 — for all eBook retail distribution
- Accessible EPUB — if distributing to academic, library, or EU markets (where EAA compliance is required)
The EPUB and print PDF are derived from the same source material but are produced differently. A print-ready PDF cannot be submitted as an eBook, and an EPUB cannot be sent to a printer.
Frequently Asked Questions
Can I just submit my PDF as an eBook on Amazon KDP?
Technically yes — KDP accepts PDF uploads — but it produces a very poor reading experience on Kindle devices. Text does not reflow, readers must zoom, and the file will receive poor reviews based on formatting alone. Always submit EPUB for eBook distribution.
What EPUB version should I use?
EPUB 3 is the current standard and is recommended for all new publications. EPUB 2 is outdated and lacks support for modern features including accessibility metadata, MathML, and audio/video. All major retailers support EPUB 3.
What is the difference between EPUB 3 and KFX?
KFX is Amazon's proprietary eBook format, used on Kindle devices and the Kindle app. When you upload an EPUB to KDP, Amazon converts it to KFX automatically. You never create KFX files directly — you submit EPUB and Amazon handles the conversion.
Is PDF more accessible than EPUB?
Not inherently. Both formats can be made fully accessible, but through different technical approaches. EPUB uses HTML semantics and ARIA roles; PDF uses tag trees and PDF/UA standards. EPUB accessibility is generally easier to implement correctly, particularly for complex content.
How large should my EPUB file be?
Most text-heavy EPUBs are under 5MB. Image-heavy EPUBs (illustrated non-fiction, fixed layout) can be 30–100MB. KDP charges a delivery fee for Kindle eBooks above 3MB, so keeping image sizes optimised matters for royalty calculations.
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Holograph Press Works produces EPUB 3, Fixed Layout EPUB, accessible EPUB, and print-ready PDFs — all from the same source file where possible. Request a quote →