EPUB vs. PDF vs. DOCX: which file to use for each job

Self-publishing involves at least three file formats, and each one exists for a different job. Using the wrong one, such as a PDF as the source for a reflowable ebook or a Word file for a print interior you haven’t checked, is an easy way to end up with a book that looks wrong to readers.

The short answer

• EPUB is for ebooks. Text reflows to fit any screen.
• PDF is for print: interiors and covers with fixed pages.
• DOCX is for editing and collaboration, and some stores accept it as an upload.

EPUB: the ebook standard

EPUB is the open standard for ebooks, and EPUB 3 is the current version. Its defining feature is that text reflows: the reader chooses the font, the size, and the margins, and the pages rearrange themselves. There are no fixed page numbers, because a “page” depends on the screen.

Where it’s used: KDP accepts EPUB uploads and converts them for Kindle. Apple Books, Kobo, Google Play Books, Barnes & Noble Press, and distribution services accept EPUB too, which makes it the most portable ebook file you can make.

What breaks in EPUB:

• References to page numbers, such as “see page 42”
• Layouts that depend on position: text boxes, columns, and side-by-side images
• Tabs or spaces used for indentation
• Manual line breaks used to control spacing
• Wide tables that don’t fit on a phone screen
• Fonts you don’t have the right to embed

Fixed-layout EPUB is a variant for books where the layout is the content: picture books, comics, and some cookbooks. Pages keep their design, and readers zoom instead of reflowing the text. Amazon’s Kindle Create can also produce fixed-layout Kindle books.

Checking it: validate EPUB files with EPUBCheck, the standard validator, and preview them in Kindle Previewer before you upload to KDP. Open the file in at least one other reading app too.

PDF: fixed pages for print

A PDF fixes every element in place, which is exactly what a printer needs and exactly what an ebook reader doesn’t.

Where it’s used:

• Print interiors: a PDF at your trim size, with fonts embedded, and bleed only if images run to the edge
• Print covers: a single PDF containing the back cover, the spine, and the front cover, sized for your page count and paper
• Direct sales and extras: workbooks, printables, and reader magnets where the fixed layout is the point

Some printers ask for a specific PDF standard, such as PDF/X, for print files. Check each printer’s file specifications before you export.

Why not for ebooks: KDP accepts PDF uploads for ebooks only in certain languages, and conversions from PDF often produce awkward line breaks and lost formatting. A reflowable ebook should start from a source that understands paragraphs and headings, such as a well-structured document or an EPUB.

DOCX: for editing, and sometimes for upload

DOCX is Microsoft Word’s format. Its strength is collaboration: tracked changes, comments, and a file nearly every editor, beta reader, and copyeditor can open.

Where it’s used:

• Editing: sending your manuscript to editors and getting it back with tracked changes
• Uploading: KDP accepts DOCX for both ebooks and paperbacks and converts it, and some distributors accept it as well

Making DOCX convert well:

• Use paragraph styles, especially a heading style for chapter titles, so a table of contents can be generated
• Use page breaks, not repeated blank lines, between chapters
• Use first-line indents from the paragraph style, not tabs
• Keep images inline with the text rather than floating

Uploading a DOCX is convenient, but you have less control over the result than with a carefully built EPUB or PDF. Preview the converted book page by page.

Other formats you’ll meet

• KPF: the format Kindle Create produces. It works only on Amazon.
• MOBI: an older Kindle format that KDP has phased out for uploads. If a guide tells you to make a MOBI file, it’s out of date.
• Markdown: a plain-text format some writers draft in. It converts easily into other formats, but it isn’t uploaded to stores directly.

Side by side

Which file goes where on KDP

For a typical self-published book on Amazon:

• Ebook manuscript: EPUB, DOCX, or KPF from Kindle Create
• Ebook cover: an image file, such as a JPG, at the dimensions KDP recommends
• Paperback interior: a PDF is the safest choice, although KDP also accepts DOCX
• Paperback cover: a single PDF with back, spine, and front, built from KDP’s template for your page count

Other stores and printers have their own lists, so check each one’s specifications before you export.

Front and back matter differ by format

In print, front matter follows a traditional order: title page, copyright page, dedication, and so on. In an ebook, the free sample starts at the beginning of the file, and every page of front matter is a page of story the sample doesn’t show. Many authors keep the ebook’s front matter short, with the title page and copyright page only, and move the dedication, acknowledgments, and other material to the back.

One manuscript, several files

The safest workflow keeps a single master manuscript and generates every format from it. When you fix a typo, fix it in the master and export again, rather than patching the EPUB, the PDF, and the Word file separately. Patched files drift apart, and readers of different editions end up with different text. Keep the exported files in dated folders, so you always know which version is live in each store.

File size affects ebook royalties

On KDP’s 70% royalty option, Amazon deducts a delivery cost based on file size: $0.15 per megabyte on Amazon.com. A novel’s text barely registers, but uncompressed images add up. Compress images to the size they’ll display at before you export. Pricing an ebook on KDP shows when file size tips the balance between royalty options.

Accessibility is part of the file

Readers who use screen readers rely on the structure inside the file. Use real headings rather than bold text, add alternative text to meaningful images, and keep the reading order logical. Accessibility requirements for ebooks have tightened in some markets, including the EU, so building the habit now saves rework later.

Pre-upload checklist

For the EPUB:

• It validates without errors
• The table of contents works and matches the chapters
• Links work, including the one to your newsletter
• Images are compressed and have alt text

For the print PDF:

• The page size matches the trim size, plus bleed if used
• All fonts are embedded
• Images are at 300 DPI at print size
• The cover dimensions match the final page count

For the DOCX:

• Styles are used for headings and paragraphs
• Tracked changes are accepted and comments removed
• There’s no manual spacing or tab indentation

For print-specific settings, see trim sizes and interior formatting basics.

AIBookWriter exports the same manuscript as a print-ready PDF, an EPUB, a DOCX, or Markdown, with preflight checks before export. Before you export, the free Copyright Page Generator drafts a copyright page you can check and paste into the front matter.