Compress Scanned PDF Documents

A regular PDF stores text as vector glyph instructions — a few bytes per character. A scanned PDF stores a full-colour photograph of each page, often at 300–600 DPI. A single A4 page at 600 DPI in colour is roughly 100 megapixels of raw data, which is why scans balloon to tens of megabytes.

No, provided you scanned printed text. Downsampling from 600 DPI to 150 DPI preserves full on-screen legibility and prints cleanly on any office printer. If you are archiving fine handwriting, faded historical documents or engineering drawings, choose Recommended or Less Compression instead.

If your scanner already added an invisible OCR text layer, structural compression preserves it. However, the Extreme preset may rebuild pages as images and drop that layer. Use Recommended mode when a searchable text layer must survive.

You can compress them, but be aware that any modification to a PDF invalidates its cryptographic signature — this is true of every compression tool, not just ours. If the signature must remain valid, do not compress the signed document.

Any modern browser with WebAssembly support: Chrome, Edge, Firefox, Safari, Brave, Opera and Arc, on desktop and mobile. Chromium-based desktop browsers are typically the fastest for very large documents.

No. Compression runs entirely inside your browser using WebAssembly. Your PDF is read into local memory, processed on your own CPU and written straight back to your downloads folder. No network request ever carries the file.

Yes, and this is usually desirable. Author names, the originating software, revision history, comment threads and XMP blocks are stripped. That reduces file size and removes information you may not want to share — a genuine privacy benefit when sending documents externally.

Page dimensions, margins and layout are always preserved exactly. Print appearance only changes if images are downsampled below your printer's resolution. Less Compression holds images near 200 DPI, which prints cleanly on any office printer; avoid Extreme mode for anything going to paper.

Yes. The interface is fully responsive and the engine runs on iOS and Android. Bear in mind that mobile devices have less memory, so very large files (over roughly 50 MB) may be slow or fail on older phones.

It depends on the content. Scanned or image-heavy documents commonly shrink by 70–95%. Text-only PDFs that were already optimized may only drop 5–20%, since there is little redundant data left to remove.