Every Way to Convert Ebooks: EPUB, MOBI, AZW3 and PDF
By the Universal PDF Team · Published · Updated · 8 min read
Converting ebooks comes down to two families: reflowable formats (EPUB, MOBI, AZW3) that adapt to any screen, and fixed-layout PDF that locks every page in place. Conversions within the reflowable family are clean; crossing into or out of PDF involves real tradeoffs. This guide covers every direction, device compatibility, and the honest limits, including DRM, which no legitimate converter can bypass.
What are EPUB, MOBI, AZW3 and PDF, really?
Four file extensions, but only two fundamentally different ideas:
- EPUBis the open industry standard for ebooks: essentially a zipped bundle of text and images that the reading app lays out live. It's reflowable: enlarge the font and the text re-wraps; switch devices and the "pages" re-paginate. Nearly every reader and store outside Amazon is built on it, and since Amazon's Send to Kindle accepts EPUB, it's the safest format to standardize on.
- MOBIis Amazon's original Kindle format, also reflowable but old. It lacks modern styling support and Amazon has retired it for new documents. It matters today mainly as the format your older files are stuck in.
- AZW3(also called KF8) is MOBI's successor: Amazon's richer reflowable format with better typography and layout support. Still Kindle-oriented, still not what other readers speak natively.
- PDF is the odd one out: fixed-layout. It records exactly where every character sits on a page of a specific size. Ideal for printing and layout-critical documents; awkward for reading on a small screen, where you zoom and pan instead of reflowing.
That reflowable-versus-fixed split is the single most useful thing to know: it predicts how well any conversion will go before you run it.
Which formats work on which devices?
| Device / app | EPUB | MOBI | AZW3 | |
|---|---|---|---|---|
| Kindle e-readers | Yes, via Send to Kindle | Legacy only (no longer accepted for new sends) | Yes (Kindle-native) | Opens, but no reflow, so the text is small |
| Kobo, PocketBook, Tolino | Yes, native | Partial or no support | No | Opens, same zoom-and-pan problem |
| Apple Books, Google Play Books | Yes, native | No | No | Yes |
| Computer (any OS) | Needs a reader app | Needs a reader app | Needs a reader app | Opens everywhere, usually in the browser |
| Printing | Poor: no fixed pages | Poor | Poor | Excellent; built for it |
The pattern is clear: EPUB is the universal reading format, AZW3 is the Kindle specialist, MOBI is legacy, and PDF is for screens-of-any-size and paper.
Which conversion do you need?
Match your situation to a direction. Every row links to the tool that handles it:
| You have | You want | Use | How it goes |
|---|---|---|---|
| EPUB | PDF (to print or annotate) | EPUB to PDF | Clean, since pagination is what readers do anyway |
| EPUB (to read comfortably) | PDF to EPUB | Good for text-first PDFs; layout-heavy ones get awkward | |
| EPUB | MOBI (older Kindle) | EPUB to MOBI | Clean (reflowable to reflowable) |
| MOBI | MOBI to PDF | Clean, same as EPUB to PDF | |
| AZW3 | AZW3 to PDF | Clean pagination from a reflowable source | |
| MOBI or AZW3 | PDF to MOBI, PDF to AZW3 | Same caveats as PDF to EPUB | |
| Comic archives (CBR) | CBR to PDF | Clean: image pages map directly onto PDF pages |
For directions not listed here (and for mixed batches), the Ebook Converter hub is the place to start: drop a file in and pick your output format.
How do I actually convert an ebook?
Every direction follows the same three steps:
- Open the tool for your direction, say EPUB to PDF, and drop your file in. Files up to 100MB are accepted, which comfortably covers almost any ebook.
- Click Convert. Your ebook uploads over an encrypted connection; most conversions finish in seconds, large image-heavy books can take a few minutes. Your files are encrypted and stay in your account — delete them anytime.
- Download the result and load it onto your device. For Kindle, use Amazon's Send to Kindle with the EPUB; for Kobo and most other readers, copy the file over USB or use the vendor's app.
Universal PDF runs on a single Pro subscription: one plan unlocks every tool on the site and covers downloading your results, with no per-tool fees and nothing to install. Current plan options are shown at checkout, and you can cancel anytime.
Which direction converts well, and which needs realistic expectations?
Reflowable to reflowable: the easy case
EPUB, MOBI, and AZW3 all describe the same thing: flowing text with images. Conversions among them are essentially repackaging. Chapters, formatting, and images come through cleanly in the normal case. If a book looks right in one reflowable format, expect it to look right in another.
Reflowable to PDF: reliable
Turning EPUB, MOBI, or AZW3 into PDF means paginating flowing text onto fixed pages, which is exactly what every reading app already does on screen. The result prints well and looks consistent everywhere. The one thing you give up is reflow itself: the PDF is committed to one page size and one font size forever.
PDF to reflowable: the honest hard case
This direction runs uphill. The converter must infer flowing paragraphs from fixed positions on a page, deciding what's a heading, what's a caption, where paragraphs actually break. Text-first PDFs (novels, essays, reports) convert nicely. Multi-column layouts, dense tables, footnotes, and diagram-heavy pages can come out with awkward breaks, and for those the PDF may simply remain the better reading copy. One hard prerequisite: scanned PDFs contain no extractable text at all. They're photographs of pages, so run them through OCR first, or the conversion has nothing to work with.
Comics and image-heavy books: a case of their own
Comics, manga, and photo books are effectively fixed-layout even when they arrive in a reflowable container: each page is one full image. That makes CBR to PDFone of the cleanest conversions there is: image pages map one-to-one onto PDF pages. Going the other way, into a reflowable format, buys you nothing, because there's no text to reflow. Keep comics in fixed-layout formats, and if the resulting PDF is too heavy to move around, run it through Compress PDF rather than switching formats.
Does converting change the file size?
Usually less than people expect. An ebook's size is dominated by its images (cover, illustrations, photos), and those travel through conversion largely as-is, so a text-first novel stays small in every format. Two real effects worth knowing: converting a reflowable book to PDFtends to grow the file somewhat, because the converter embeds fonts and commits every page's layout; and image-heavy books are big in every format, because the pictures are the payload. If a converted PDF needs to fit under an email limit, compress it afterwards. That's a separate, well-understood step.
Can you convert DRM-protected books?
No, and we want to be straightforward about this rather than let you burn a conversion finding out. Books bought from the Kindle store or Apple Books, and books borrowed through library apps like Libby, are usually locked with DRM (digital rights management). Our converters cannot open DRM-protected files, and we do not remove or bypass DRM in any direction: the conversion will simply fail. This is true of every legitimate conversion service, whatever their marketing implies. What converts without any issue: DRM-free ebooks, which includes everything from Project Gutenberg and Standard Ebooks, many independent publishers and DRM-free storefronts, and any book you wrote or produced yourself.
What happens to metadata and covers?
Ebook files carry more than the book: title, author, series, description, and a cover image travel inside the file as metadata. Reasonable expectations by direction:
- Between reflowable formats, core metadata (title, author, cover) generally carries over, since EPUB, MOBI, and AZW3 all have standard places for it.
- Into PDF, the cover typically becomes the first page, which is usually what you want for reading and printing. PDF's own metadata fields are simpler than an ebook's, so richer details like series information may not survive.
- Out of PDF, expect to tidy up afterwards. PDFs often carry sparse or wrong metadata (a filename as the title, no author), and the conversion can only pass along what's there. Most reading apps let you edit title and author after import, and it's worth a minute for a book you'll keep.
Which format should you keep your library in?
If you maintain a collection of DRM-free books, it pays to standardize rather than hold a mix of formats. The practical recommendation:
- Keep text-first books as EPUB.It's the open standard, every modern device accepts it (Kindle included, via Send to Kindle), and it converts cleanly to anything else if a device someday demands a different format. An EPUB library is the most future-proof library.
- Keep layout-critical books as PDF. Manuals, sheet music, textbooks with precise figures, and comics lose something real when reflowed. If the pages were designed as pages, preserve them.
- Convert legacy MOBI and AZW3 files to EPUB-era formats when you touch them. There's no urgency, since the files still work, but each old format you retire is one less special case in your library. The Ebook Converter handles the migration a file at a time.
One habit borrowed from every good backup strategy: keep the original file after converting. Conversions between reflowable formats are clean, but they are interpretations, not exact copies. And storage is far cheaper than discovering years later that the only surviving copy is the converted one.
The short version
Standardize on EPUB for reading: every modern device accepts it, including Kindle via Send to Kindle. Convert to PDF when you need printing or a locked layout; convert PDFs to reflowable formats only when they're text-first, and OCR scans before trying. DRM-protected purchases can't be converted by us or anyone legitimate. For everything else, pick your direction above or start at the Ebook Converter. Each conversion takes a few seconds.