How to use the Compress PDF
- Add the PDF files that are too large.
- Choose Light, Recommended or Strong. Start with Recommended and only go to Strong if the portal still says the file is too big.
- Press Compress. The new size and the saving appear next to each file, so you can see at once whether it now fits under the limit.
- Open the result and zoom in on a scanned page before you submit it.
The three levels in numbers
Light rewrites JPEG images at quality 82 and shrinks any picture longer than 3000 pixels on a side; lossless images stay as they are. Recommended drops to quality 70 with a 2000-pixel cap and also converts large lossless images to JPEG. Strong goes to quality 50 with a 1400-pixel cap.
A picture is swapped only when the new one is at least 5% smaller. If the finished PDF is not smaller than the one you added, you get the original back rather than a heavier copy.
Scans versus typed documents
Phone and office scanners usually save each page as a high-resolution photo, which is why a ten-page scan can reach 30 MB. Those files shrink the most, frequently by well over half.
A letter exported from a word processor is mostly text and fonts, with little to recompress, so expect a small saving. Logos with transparency, CMYK artwork, black-and-white fax-style scans and JPEG 2000 images are skipped to protect their colours and edges.
Questions
Can people still search and copy the text?
Yes. Only embedded images are touched; the text layer, links and fonts are written back unchanged.
Should I compress a file that will be printed?
Keep the original for print and send a compressed copy by email. Strong in particular can soften fine detail at printing resolution.
Is my document uploaded?
No. The images are re-encoded with MozJPEG compiled to WebAssembly, inside this tab.