EPUB & Print Formatting: A Technical Guide

"Formatting" looks simple from the outside, but a retail-ready book is really two different technical deliverables: a reflowable EPUB for eBook stores and a fixed, print-ready PDF for paperback and hardcover. Get the underlying structure right and your book uploads cleanly, renders consistently, and reads beautifully everywhere.

1. Reflowable EPUB: structure over styling

An EPUB 3 file is essentially a zipped website: XHTML content documents, CSS, images, and metadata bound together by a package (.opf) file and a navigation document. Reflowable means the reader app — not you — controls font size, margins, and page breaks. Your job is to provide clean, semantic structure so the reader can reflow it gracefully.

The single most common mistake is styling with direct formatting (manual line breaks, tabs, multiple spaces) instead of semantic styles. Use real heading levels and paragraph styles:

<h1>Chapter One</h1>
<p class="first">The opening paragraph, no indent.</p>
<p>Subsequent paragraphs, first-line indent via CSS.</p>

Indents, spacing, and chapter breaks belong in CSS, not in the text:

p { margin: 0; text-indent: 1.2em; line-height: 1.5; }
p.first { text-indent: 0; }
h1 { page-break-before: always; text-indent: 0; }

Navigation & metadata

Every EPUB needs a navigation document (the logical table of contents) with correctly nested links, plus complete metadata: title, author, language, and a unique identifier. A working TOC is both a usability feature and a frequent cause of retailer rejection when missing.

2. Fonts, images, and accessibility

• Fonts: prefer the reader's default serif for body text; only embed fonts when the design truly requires it, and confirm you are licensed to embed them.
• Images: use RGB, size them to roughly 2x their display width, and keep file sizes modest. Always include alt text for accessibility.
• Accessibility: logical reading order, real headings, and alt text aren't optional niceties — they widen your audience and are increasingly expected by stores.

3. Validate before you upload

Run your file through EPUBCheck (the official validator). A file that passes EPUBCheck and previews cleanly in Kindle Previewer and Apple Books will sail through retailer ingestion. Test on at least one e-ink device and one phone, at the smallest and largest font sizes, to catch reflow surprises.

If it isn't semantic, it isn't reflowable. Structure first, style second.

4. Print: a fixed, unforgiving medium

Print is the opposite of reflowable — every page is locked. You design to an exact trim size (e.g., 5"×8", 6"×9"), with margins and gutter chosen for the page count, because thicker books need a wider gutter so text doesn't disappear into the spine.

Watch the typographic details print exposes mercilessly: widows and orphans, loose or tight lines, consistent running heads, and chapters that start on the correct (usually right-hand) page. Export to PDF/X-1a with all fonts embedded and images flattened so the printer reproduces exactly what you approved.

5. One manuscript, two pipelines

Because the requirements diverge, professional formatting maintains a single source of truth (your final, proofread text and a style sheet) and produces both outputs from it — never copy-pasting between them, which reintroduces errors. The eBook is validated with EPUBCheck; the print PDF is preflighted and a physical or digital proof is reviewed before the book goes on sale.