Everything else follows from one distinction, so it is worth being precise about it.
Fixed versus reflowable
A PDF is a description of pages. Page seven is page seven on a phone, on a laptop and coming off a press — the same line breaks, the same position for every word. That is the entire point of the format: it was invented so a document would look identical everywhere.
An EPUB has no pages until someone opens it. It is closer to a small website in a box: the reading app takes your text and lays it out for the screen it is on, at the type size the reader chose. Someone reading at large type on a phone gets more, shorter pages than someone on a tablet, and both are correct.
What survives in each
| EPUB | ||
|---|---|---|
| Page size | Fixed, chosen by you | None — it reflows |
| Line breaks | Exactly as set | Decided at reading time |
| Your typefaces | Embedded in the file | Packaged with the file |
| Colours and heading styles | Exact | Carried over |
| Page numbers | In the footer | Not applicable |
| Cover artwork | First and last pages | The file's native cover |
| Reader can change type size | No | Yes |
| Reader can use a dyslexia font | No | Usually |
The last two rows are worth pausing on. In an EPUB the reader controls type size, line spacing and often the typeface itself. Some authors find this uncomfortable — you designed the page, and the reader can overrule you. It is also what makes an ebook readable to someone with low vision, and refusing them that is not a design decision worth defending.
Choose by destination
Choose PDF when
- It will be printed, by you or by anyone else.
- It is a workbook or worksheet with blanks to fill in — the layout is the content.
- It is a lead magnet where the design carries the impression. Most people open these on a laptop, where a PDF is fine.
- The layout is load-bearing — diagrams with labels, tables, anything positional.
- You need it to be identical for everyone, for legal or brand reasons.
Choose EPUB when
- It is going into a store — Apple Books, Kobo, Google Play Books all want EPUB.
- It is mostly prose, read start to finish. Fiction, memoir, essays.
- Your readers are on e-readers or phones.
- Accessibility matters, which it always does, and increasingly it is a legal requirement rather than a courtesy.
Why the answer is usually both
These are not competing formats; they are the same book for two situations. A pattern that works for almost everyone publishing independently:
- EPUB as the file you sell or list in stores.
- PDF as the file you hand out directly — the lead magnet, the review copy, the version a client prints.
- PDF again, at whatever specification the printer asks for, if the book goes to paper.
That is three files from one manuscript, which is only reasonable if producing them is close to free. It is the argument for keeping the source in something format-neutral — Markdown, say — rather than in a layout application where the file *is* the PDF and the ebook has to be rebuilt by hand.
The practical trap
The mistake is designing for one and exporting the other. A PDF laid out with tight, deliberate page breaks becomes a strange EPUB, because those breaks no longer mean anything. An EPUB-first manuscript with no thought given to pages becomes a PDF where chapters start halfway down.
The way out is to mark up the manuscript by structure — this is a chapter, this is a heading, this starts a new page — and let each format interpret that structure in its own terms. Structure survives the trip; layout does not.
That is how bukpress handles it: one Markdown file, one set of design decisions, and both files come out of it. Your typefaces, colours and heading rules carry into the EPUB; the cover you upload becomes the PDF's first page and the EPUB's native cover. EPUB export is on the Pro plan — see pricing — and PDF is on every plan including the free one.
If you are still deciding, the sample book is the PDF half, and it will tell you more in two minutes than another comparison table will.