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Compress PDF
Compress PDF rebuilds a PDF with rasterised page images encoded at a lower resolution and quality, which is what actually removes most of the weight from scanned and image-heavy documents. You choose between a balanced and an extreme preset, and the tool reports the before/after size.
How to use Compress PDF
- Upload the PDF and wait for the page count to be read.
- Pick the Recommended preset for a good size/quality balance or Extreme for the smallest possible file.
- Run the compression and compare the reported original and compressed sizes before downloading.
Where Compress PDF is useful
- Getting a scanned contract under an email attachment limit.
- Reducing a photo-heavy brochure for web distribution.
- Shrinking archive copies of paperwork that only needs to stay legible.
Formats, algorithms and limits
Pages are rendered through PDF.js and re-encoded as images: Recommended uses roughly 1.35× scaling with 0.70 JPEG quality, Extreme uses native scale with 0.45 quality. Text stops being selectable in the compressed output, which is how the largest savings are achieved.
Troubleshooting and honest limits
- If you need to keep selectable text, keep a copy of the original — compression rasterises pages.
- Extreme mode is tuned for legibility of large print; small footnotes may soften noticeably.
- Documents that are mostly text and already well optimised may shrink very little, because there is no image data to re-encode.
Frequently asked questions
Why did my file only shrink a little?
Compression works by re-encoding page images. A text-only PDF that is already optimised has almost no image data to shrink, so savings are naturally small.
Will text still be selectable after compressing?
No. Pages are rasterised during compression, so text becomes part of the image. Use compression for distribution copies and keep the original for archiving or editing.
Which preset should I choose?
Recommended keeps most detail and is fine for contracts and reports. Extreme targets the smallest file and is best for scans whose main content is large print.
Can I compress a password-protected PDF?
No — the parser needs to read every page to rasterise it. Unlock the document first, then compress the decrypted copy.
Related tools
Page written and reviewed by the FreeConvertio engineering team on 2026-10-14. Compress PDF runs entirely in your browser — no uploads, no account and no daily limits.