EPUB vs print PDF: what each file is for

An EPUB and a print PDF are both "the book," and they are formed in different ways. An EPUB has no fixed page size and no page numbers, because the reader decides the font and the type size. A print PDF has an exact page size measured in inches, with margins, running heads and page numbers baked into it, because it is going on paper.

Almost every formatting problem an author hits before uploading comes from treating one of those files as if it were the other. Here is what each one is, what breaks when you confuse them, and how to check both before you send them anywhere.

EPUB is Reflowable

An EPUB is closer to a small website than to a printed page. It contains your text marked up with structure, plus a stylesheet describing how that structure should look, and the reading device does the layout at the moment of display.

That means the reader is in charge of several things you might expect to control:

• Font. The reader picks it, or the device picks a default. You can suggest one, and many readers will honor it, but a reader who prefers a larger serif face gets a larger serif face.
• Type size. Adjustable by the reader, usually with a slider.
• Line length and margins. Determined by the screen and the reader's settings.
• Page count. There isn't one. The same EPUB might be 190 screens on a phone and 84 on a tablet.

Because the page does not exist as a fixed object, page numbers do not exist either. Neither do "see page 47" cross-references, running heads, or any instruction that depends on where something physically sits.

What you design instead is structure. You mark a heading as a heading, a block quote as a block quote, an epigraph as an epigraph, and a scene break as a scene break. Then you style those roles and the device arranges them. Your job is to describe what each piece of text is, not where it goes.

This is why a clean EPUB comes from a clean manuscript. If you created a chapter heading by typing the title in a bigger font and centering it by hand, the file has no idea it is a heading. The table of contents will not find it, and a reader jumping between chapters will not be able to.

Print PDF is Fixed

A print PDF is the opposite in every respect. It is a page of an exact physical size with everything positioned on it, and nothing moves after export.

You are responsible for all of it:

• Trim size. The finished dimensions of the book, 5.5 by 8.5 inches, 6 by 9 inches, or whatever your printer accepts. This is a decision you make before layout, not after, because it determines how much text fits on a page.
• Margins. The white space on all four sides, which affects both readability and page count.
• Gutter. Extra inside margin to account for the binding. Without it, text near the spine disappears into the fold, and the thicker the book the more gutter it needs.
• Running heads. The author name and book title, or chapter title, repeated at the top of pages. Conventionally suppressed on chapter openers and blank pages.
• Page numbers. Placement, style, and where numbering starts. Front matter is often numbered separately or not at all.

And one requirement that has no equivalent in EPUB: the fonts must be embedded in the file. A print PDF that references a font instead of containing it will render with a substitute at the printer, and you will not find out until you see the proof. Embedding also requires that the font's license permits it, which is worth checking for anything you did not get from a source that states embedding rights clearly.

Failure Points

The failures are consistent and easy to recognize once you know what you are looking at.

Hard page breaks in an EPUB. If you forced a page break to push a chapter to a new page in a print layout, it becomes a stray blank screen in the ebook, or a chapter that starts halfway down.

Manual line breaks in poetry or addresses. These survive into the EPUB and then collide with the reader's larger type size, producing ragged half-lines that look like errors.

Fixed indents and tabs. A tab character does not mean the same thing at every type size. Paragraph indentation in an EPUB should come from the stylesheet, not from tabs you typed.

Page-number references. "As discussed on page 112" is correct in print and meaningless in an EPUB. In an ebook the equivalent is a link.

A print PDF exported at the wrong trim. Exporting a manuscript at US Letter and then asking a printer for a 6 by 9 book produces either a rejection or a scaled interior with type that is subtly the wrong size and margins that are wrong in a way readers feel without identifying.

Missing gutter. The most common print error. It looks fine on screen, because on screen there is no spine.

Retailer Requirements

Every retailer publishes its own current spec, and you should check it rather than trusting a blog post, including this one.

Ebook stores take EPUB. Kobo, Apple Books and Google Play all work from EPUB, and Amazon accepts EPUB for Kindle and converts it on their end. One well-built EPUB generally serves all of them.

Print is where the requirements get specific. Print-on-demand services want a PDF at the exact trim size, with fonts embedded, and they each have their own rules about bleed, minimum margins, and how the interior file relates to the cover file. A 6 by 9 interior for one printer is not automatically acceptable to another. Read the current spec for the printer you are actually using, and read it before you lay the book out, not after.

Images and Tables Behave Differently

Images are where the two formats diverge most visibly.

In an EPUB, an image is placed in the flow of text and scales to the reader's screen. A full-page illustration on a tablet is a postage stamp on a phone. Wide images get scaled down until the detail is gone. Text inside an image cannot be resized by the reader, cannot be searched, and cannot be read by a screen reader, so an image of a chart is a poor idea in an ebook.

In a print PDF, an image sits at a fixed size and position, and its resolution has to be adequate for print. An image that looks sharp on screen at 72 pixels per inch will look soft on paper. Print wants substantially more resolution than a screen does.

Tables are harder in EPUB than most people expect. A table has an inherent width, and reflowable text does not. A four-column table that reads well on a tablet will either be cut off or squeezed into illegibility on a phone. If your book has real tabular data, consider whether it can be restructured as a list for the ebook, and keep the table for print.

Check Both Files Before You Upload

A short routine catches most of it.

For the EPUB: open it on the smallest screen you have, then set the type size to the largest option. That combination exposes broken line breaks, tables that do not fit, and images that were sized for a tablet. Walk the table of contents and confirm every chapter is in it and every link lands. Check that the cover appears and that front matter is in the right order. Run it through an EPUB validator, which will catch structural problems the eye will not.

For the print PDF: check the page size in your PDF reader's document properties and confirm it matches the trim you ordered. Confirm fonts are embedded, which the same properties panel will tell you. Print a few pages at 100 percent on paper and hold them, since margin problems are much easier to see physically than on a screen. Look specifically at chapter openers, the first page after each break, and any page with an image, because those are where layout errors cluster. Then check the page count against the printer's minimum and maximum.

Both files come out of the same manuscript, so it is reasonable to expect them to come out of the same software. In Calamus, Compile produces the EPUB and the print PDF at real trim sizes from one source, along with DOCX and Markdown, with typefaces licensed for embedding in books you sell. Making a structural change once and re-exporting both is a different working pattern than fixing the same typo in two places. The rest of what the app does with a manuscript is on the book writing software page.

Whatever you produce them with, the underlying rule holds. Design the EPUB by describing structure, design the print PDF by controlling position, and do not ask either file to do the other one's job.