How to reduce PDF file size
If your PDF won't attach to an email or an application site says "file too large", the fix usually takes a few minutes. This guide explains why a PDF is big and how to make it smaller with as little quality loss as possible.
Why are some PDFs so large?
Images decide the size of a PDF. A 20-page text-only PDF is often just a few hundred KB, while a single page photographed with a phone or scanned on a scanner can be several MB on its own, because the page is really a high-resolution photo.
That is why scanned documents, presentations with photos and phone pictures turned into PDFs shrink the most. A PDF made only of text is already small and won't shrink much.
Check the limit first
- Email: Most email services allow attachments of about 20–25 MB. The recipient's service may accept less, so aim for under 10 MB if you are not sure.
- Job, university and government portals: Each site sets its own limit, usually shown next to the upload field. Note it and aim slightly below it.
Step by step
- Open the Compress PDF tool and choose your file.
- Start with the Balanced level and press Prepare. The tool shows the old and new size.
- If the file is still above the limit, try the Strong level. At both levels text, links and layout stay intact; only images get smaller.
- As a last resort use Maximum. Pages are turned into images and text can no longer be selected. That is fine for scanned papers, but not for documents someone needs to copy text from.
Still too big? Three more ways
- Remove pages you don't need. Blank backs and extra attachments add size for nothing. Delete them with Delete PDF pages, then compress again.
- Turn colour scans grey. If colour doesn't matter, grayscale can cut the size noticeably. The result is image-based, so text can't be selected.
- Split the file. If the portal accepts several files, use Extract pages to split the document into two or three parts.
ID cards, diplomas, medical papers: privacy
The files people need to shrink are often personal: ID copies, diplomas, bank statements or medical reports. Many free PDF sites upload your file to their server to process it. On ManamoPDF compression runs entirely in your browser; your file never leaves your device.
Frequently asked questions
Will compression ruin the quality?
At the Balanced level images shrink in a way that is hard to notice on screen or in print. At Strong, small text in scans may look slightly softer. Open the result and make sure it is readable; if not, go back one level.
My file didn't get smaller. Why?
If the PDF is mostly text, there are no images to shrink. When the result isn't smaller than the original, the tool keeps your file and tells you. Try the extra methods above.
Does it work on a phone?
Yes. There is no app to install; open the page in your phone's browser and choose the file. Very large files take longer on a phone.
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Last updated: 7 November 2026