EPUB is the universal format for e-books: Project Gutenberg's 70,000+ public domain books are distributed as EPUB, library lending platforms use it, and most independent publishers distribute directly in EPUB. Converting an EPUB to PDF lets you print a book, annotate it in a PDF-native tool, read it in environments where EPUB is not supported, or archive a snapshot with fixed pagination.
The DRM problem
Most commercial e-books from publishers, Amazon Kindle (MOBI/AZW, not EPUB natively), Apple Books, and library lending platforms include DRM — Digital Rights Management — which encrypts the file. Only the licensed reading application (Kindle app, Apple Books, etc.) can decrypt and display the book. LibreOffice, Calibre, and every other converter tool cannot read a DRM-protected file.
The books you can convert are: DRM-free EPUB files purchased directly from publishers (Tor Books, O'Reilly, Humble Bundle, and others sell DRM-free), books from Project Gutenberg (public domain, no DRM), EPUB files you created yourself (exported from a writing tool), and books from stores that specifically advertise DRM-free sales (Smashwords, Book View Cafe, many independent publishers).
If a conversion attempt results in an error or an empty PDF, the file is almost certainly DRM-protected. The converter is not broken — it cannot read content it is not licensed to read.
Formatting and reflowable text
EPUB is designed to be reflowable: the text wraps to fit whatever screen you are reading on, at whatever font size you choose. This is fundamentally different from PDF, which has fixed pages, fixed margins, and fixed font sizes.
When an EPUB is converted to PDF, the reflowable text is paginated using LibreOffice Writer's default paper size (A4 or US Letter depending on the server locale) and its default font. The text will look different from your e-reader. The content is correct — every word is there — but the line breaks and page breaks are different.
For public domain texts and technical documentation, this is usually acceptable. For books where the original typographic design matters — illustrated books, poetry with precise line breaks, books with specific layout elements — the PDF output will not preserve that design.
Using Filum's EPUB to PDF tool
Upload the EPUB file. Filum sends it to a LibreOffice Writer server, which opens the EPUB file and exports it as PDF. The file is sent over an encrypted connection, converted, and immediately deleted — it is never stored permanently. No account is required.
Conversion time depends on the book's length and complexity. A typical novel converts in 15–25 seconds. A long non-fiction book with many embedded images may take up to 45 seconds.
Alternatives for DRM-free books
Calibre is the open-source e-book management and conversion tool that converts between every e-book format including EPUB, MOBI, and PDF. It is free, powerful, and produces high-quality output — but requires installation on your computer. If you are working with large numbers of files or need precise control over the output format, Calibre is the right tool. Filum is the right tool when you need one book converted in the next two minutes without installing anything.