PDFs balloon for predictable reasons: high-resolution scanned images, embedded fonts you don't need, redundant object streams, or simply because the producing application didn't optimize. The right compression strategy depends on what's actually making your file big.
Two kinds of compression
Lossless compression reorganizes the PDF's internal structure: it removes unused objects, compresses streams with zlib, and deduplicates fonts. The visual result is identical, and you typically save 10–30% on text-heavy PDFs.
Lossy compression re-encodes embedded images at a lower JPEG quality and downsamples them. For scanned documents this can shrink a 50 MB file to 3 MB without any noticeable difference at screen resolution — but the savings come at the cost of detail.
Choosing a quality level
- Screen (72 DPI, ~60% JPEG quality) — sharing by email, embedding in a chat, attaching to a web form.
- eBook (150 DPI, ~75% quality) — reading on a tablet, archiving documents you'll re-open often.
- Print (300 DPI, ~85% quality) — anything you'll send to a print shop.
Try it
Our Compress PDF tool runs entirely in your browser. Upload a file, pick a quality preset, and compare the before/after size on the spot. Nothing is uploaded to a server.
When compression doesn't help
If your PDF is mostly vector text and the file is already large, the bottleneck is usually embedded fonts. Try flattening the document or removing unused fonts via a "PDF/A conversion" workflow. If the file contains form fields and annotations you no longer need, flattening can also help by merging interactive layers into the page content.