None of these three formats is objectively "correct" for a novel. Each one is built for a different destination, and picking the wrong one for a given step, agent submission, self-publishing, print, creates problems that have nothing to do with the writing itself.
DOCX: for editing, submission, and collaboration
DOCX (Microsoft Word's format) is what you want for anything involving another person reading and responding to your text: literary agent submissions, editor feedback, beta reader comments. It supports track changes, comments, and easy editing, and it's the format most submission guidelines explicitly ask for unless stated otherwise. It's also the format most import and conversion tools expect as a starting point.
PDF: for a fixed, final look
PDF locks in exactly how a document looks, page by page, regardless of what software or device opens it. That makes it the right choice when you need something to look identical everywhere: a formatted manuscript sample where layout matters, or interior files for KDP print formatting, where Amazon's own guidance recommends converting to PDF before uploading for the most reliable result. What PDF isn't good for is easy editing or commenting; it's a final, not a working, format.
EPUB: for ebook reading
EPUB is the standard ebook format, reflowable text that adapts to whatever screen size and font settings a reader has chosen, rather than a fixed page layout. It's what you need for ebook distribution, and it's specifically what current KDP uploads require: Amazon stopped accepting the older .mobi format in March 2025 and now converts uploaded EPUB files internally to its own reading format.
Matching the format to the moment
| Situation | Format |
|---|---|
| Querying literary agents | DOCX (unless told otherwise) |
| Sharing with beta readers or an editor | DOCX |
| KDP ebook upload | EPUB |
| KDP print interior | |
| A fixed-layout sample to send as-is |
One manuscript, the right export for each step
Since a single manuscript often needs to become several of these formats at different points, from a DOCX for querying to a PDF for print, having a source file that exports cleanly to both without extra reformatting saves real time. Quillen exports directly to Word (.docx) and PDF, both matching the same industry-standard formatting shown in the editor, so switching between the two for different purposes doesn't mean reformatting from scratch each time.
Common questions
Does Amazon KDP still accept MOBI files?
No. Amazon stopped accepting .mobi uploads for KDP in March 2025. Upload an EPUB instead; Amazon converts it internally to its own reading format.
Should I send agents a PDF or a DOCX?
DOCX, unless an agent's submission guidelines specifically ask for something else. It's the format agents and editors can open, comment on, and track changes in directly, which a PDF makes considerably more awkward.