Compressing
How to Compress a PDF Without Losing Quality
Shrink a PDF while keeping it readable. What compression actually removes, how far you can push it, and how to check the result before you send it.
"Without losing quality" needs a small correction: compression that makes a real difference to file size does discard something. The useful question is whether it discards anything you can see.
On a scanned document, the answer is usually no — you can cut 80% of the size with the text still perfectly crisp. On a photographic brochure, the answer is yes, and you need to be more careful.
Compress a PDF
- 1Open the Compress PDF tool and add your file.
- 2Pick a level. Start conservative; you can always go further.
- 3Compare the result with the original at 100% zoom before you use it.
- 4If it is still too large, step up one level rather than jumping to maximum.
What compression actually does
Nearly all of the size in a large PDF is images, so nearly all of compression is about images. Three things happen:
- Downsampling: a 600 DPI image is reduced to 150 DPI, throwing away pixels you were never going to see on screen.
- Re-encoding: images are recompressed as JPEG at a lower quality setting.
- Structural clean-up: duplicate resources merged, unused objects dropped, fonts subset to the characters actually used.
The last of these is genuinely lossless and sometimes recovers a surprising amount on files that have been edited repeatedly.
What you can expect
| Document type | Typical reduction | Risk |
|---|---|---|
| Scanned text pages | 70–90% | Very low — text stays legible |
| Report with a few photos | 40–70% | Low at moderate settings |
| Photo-heavy brochure | 30–60% | Visible softening if pushed |
| Pure text document | 5–15% | None, but little to gain |
| Already-compressed file | Almost nothing | You are re-compressing damage |
Check it properly
- 1Open the compressed file next to the original at 100% zoom.
- 2Look at the smallest text on the busiest page — that is where damage appears first.
- 3Check any photographs for blocky artefacts in smooth areas like skies and skin.
- 4If it will be printed, print one page. Screen quality and print quality are not the same test.
- 5Confirm the text is still selectable — if it is not, the tool rasterised your pages.
Never compress twice
JPEG damage accumulates. Compressing an already-compressed file re-encodes artefacts as if they were detail, so you lose quality for very little size. If the result is not small enough, go back to the original and compress it harder in one pass.
Do it now
Compress PDF
Reduce file size while maintaining quality. It runs in this browser tab — your file is not uploaded anywhere.
Open Compress PDFFrequently asked questions
Is PDF compression lossless?+
The structural part is. The part that produces real savings — downsampling and re-encoding images — is lossy by design.
How much smaller can a PDF get?+
Scanned documents routinely lose 70–90%. Text-only files barely move, because they were already small.
Will compression make my text blurry?+
Not if the text is real text — it is not an image and is untouched. In a scan, the text is part of the image, which is why heavy settings can soften it.
Can I undo compression?+
No. Keep the original.
Why did my file barely shrink?+
Either it was already optimised, or it is genuinely mostly text. There is nothing to remove.