How to Convert PDF to DjVu (Compact Archives of Scanned Books)

If you keep a library of scanned books — old textbooks, out-of-print manuals, family documents digitised page by page — you've probably noticed that scan PDFs are huge. A 400-page book scanned at 300 DPI easily lands at 150–400 MB, because each page is stored as a photograph.

DjVu attacks exactly this problem. It separates each page into layers — the sharp black text mask, the background paper texture, and any pictures — and compresses each layer with a method suited to it. On scanned text, that layered approach routinely beats PDF's image compression by a wide margin, which is why large scan archives and digital libraries adopted DjVu in the first place.

This guide shows how to do the conversion in a browser, what the format genuinely wins you, and — just as important — the cases where you should leave your files as PDF.

When PDF to DjVu makes sense

• Archiving scanned books you want to keep long-term without burning disk space.
• Collections of scans — hundreds of files where the per-file savings multiply.
• Mostly-text scans: black text on paper is where DjVu's compression shines.

And when it doesn't: a born-digital PDF (exported from Word, InDesign, a reporting tool) is already compact vector text. Converting it to DjVu rasterises those crisp pages into images — you lose quality and often gain nothing in size. For those files, Compress or our guide on making a PDF smaller is the right tool.

How to convert PDF to DjVu — step by step

🔒 pdfty.com/en/tools/pdf-to-djvu

The honest part: you'll need a special viewer

This is the single biggest reason DjVu never replaced PDF, and you should weigh it before converting anything you plan to share:

• Browsers don't open DjVu. Chrome, Firefox, Safari and Edge all open PDFs natively; none of them opens .djvu without an extension.
• Phones and email previews generally show a DjVu attachment as an unknown file.
• You need a dedicated viewer: SumatraPDF or WinDjView on Windows, DjView (DjVuLibre) on macOS and Linux, Okular on Linux, EBookDroid or similar on Android.

For a personal archive that you read, installing one viewer once is a non-issue. For files you send to clients, colleagues or officials, it's a real barrier — convert back with DjVu to PDF before sharing, or keep a PDF copy alongside.

DjVu vs PDF for scanned books

If an institution will ever audit your archive, note that the formally recognised archival format is PDF/A, not DjVu — see PDF to PDF/A. DjVu wins on size; PDF/A wins on official acceptance.

Free local alternatives

If you'd rather convert on your own machine, the honest truth is that the open-source tooling is exactly what powers most converters:

• pdf2djvu (Linux, Windows; macOS via Homebrew): pdf2djvu -o book.djvu -d 300 book.pdf. Free, scriptable, great for batch-converting a whole folder.
• DjVuLibre ships the companion tools (ddjvu, djvm) for viewing, splitting and merging DjVu files.

There's no built-in route in macOS Preview or LibreOffice — neither writes DjVu. The browser tool exists for exactly that gap: no package manager, no command line, works the same on any OS.

Practical gotchas

• Searchability depends on the source. If your PDF already has an OCR text layer, the conversion carries it into the DjVu as hidden text. If it's a raw image-only scan, the DjVu will be image-only too — run OCR on the PDF first (our free OCR roundup compares the options), then convert.
• It's a raster format. Every page is rendered to an image at 300 DPI. Vector graphics, form fields, links and selectable born-digital text don't survive as objects.
• Savings vary with content. Clean black-on-white text compresses spectacularly; full-colour photo pages compress far less. A photo-heavy PDF may end up barely smaller.
• Size limits: free uploads are capped at 20 MB and 50 pages, which a long book scan will exceed — Split it into parts, or use Pro (no limits, $9/mo).

Frequently asked questions

Will the DjVu file really be smaller than my PDF?

For scanned text pages, usually yes, and often substantially — that's the format's whole reason to exist. For photo-heavy or born-digital PDFs the gain shrinks or disappears. Convert one representative file and compare before committing a whole library.

Does the text stay searchable?

Only if the PDF had a text layer to begin with. The converter copies an existing (OCR'd) text layer into the DjVu as hidden text. Image-only scans stay image-only — OCR the PDF first.

What DPI does pdfty use?

300 DPI — the standard for readable, printable scanned text. It's a fixed, sensible default rather than a tweakable knob.

Can I convert DjVu back to PDF later?

Yes — DjVu to PDF does the reverse, and that direction is free. The round trip keeps the page images, but remember both directions are raster conversions, so don't treat it as lossless editing.

How do I open a DjVu file on my phone or Mac?

macOS: DjView (part of DjVuLibre). iOS/Android: a DjVu-capable reader app such as EBookDroid (Android) or any reader listing DjVu support. There's no built-in support on either platform.

Is PDF to DjVu free on pdfty?

No — it's one of the Pro tools ($9/mo, unlimited use). The free tier covers most other tools at 10 operations/day, 20 MB and 50 pages per file, and DjVu to PDF is free. No sign-up is needed for free tools, and nothing gets a watermark.

Is DjVu safe for long-term archiving?

The format is open and the DjVuLibre tools are open source, so your files won't be orphaned. But viewer development has slowed, so a belt-and-braces archive keeps the master PDF (ideally PDF/A) and uses DjVu as the compact reading copy.

What happens to my uploaded book?

It's processed, then automatically deleted from storage after 1 hour. We don't read, index or log the contents of your files.