How to compress a PDF
- Add your PDF. Drag it into the box or tap Choose PDF. You can add several at once.
- Pick a level. Recommended suits most files. Use Strong when you need it smaller still, or Maximum for scanned documents that must fit a strict upload limit.
- Compress and download. Click Compress PDF. Each file shows its old and new size.
Why are some PDFs so big?
Almost always it's the pictures. A PDF made from phone photos or a scanner can contain full-resolution images of 3–12 megapixels on every page – far more detail than you need to read or print the document. Text and drawings, by contrast, take up very little space.
ConvertKettle finds the photos inside your PDF and saves them again at a sensible resolution and quality. Everything else – text, fonts, lines, links – is left exactly as it was, so the document still looks crisp and you can still search and copy the text.
Which level should I choose?
| Level | What happens | Best for |
|---|---|---|
| Light | Photos kept large and high quality | Documents you'll print |
| Recommended | Good balance of size and quality | Email and most uploads |
| Strong | Photos made smaller and lighter | Strict upload limits |
| Maximum | Every page saved as a compact image | Scans that still won't fit |
Got loose photos rather than a PDF? Shrink them with Compress Image, then turn them into a PDF with JPG to PDF. Need to put files together first? Use Merge PDF.
Frequently asked questions
How much smaller will my PDF get?
It depends on what's inside. PDFs made from scans or phone photos often shrink by 50–90%. PDFs that are mostly text are usually already small and may not shrink much.
Will the text in my PDF still be sharp?
Yes with the Light, Recommended and Strong levels – only the pictures are made smaller. The Maximum level turns each page into an image, so text can no longer be selected or searched.
Is my PDF uploaded?
No. Compression happens inside your browser, so your PDF never leaves your device.
Why didn't my PDF get smaller?
The PDF may already be well compressed, or contain mostly text and drawings rather than photos. Try the Maximum level for the biggest reduction.
Can I compress a password-protected PDF?
Not at the moment. Remove the password in your PDF reader first, then compress it.
Common PDF size limits
| Where you're sending it | Typical limit |
|---|---|
| Gmail | 25 MB per email |
| Outlook.com | 20 MB per email |
| Job application portals | Often 2–10 MB per file |
| School, court and government upload portals | Often 5–25 MB per file |
Limits vary by site, so check the number on the page you're uploading to. Recommended compression gets most scanned documents well under 10 MB.
Tips for smaller scans in the first place
- Scan at 200–300 DPI. Higher settings make huge files without making text easier to read.
- Use grayscale or black and white for text-only documents – color scans can be several times larger.
- Scan straight to PDF instead of taking full-resolution photos when you can.
- Compress photos before converting. If you're making a PDF from phone pictures, run them through Compress Image first.
Will compressing affect a signed or official document?
Light, Recommended and Strong only re-save the pictures inside the PDF; the text and layout stay the same and remain searchable. Digital signatures are a special case: changing a digitally signed PDF in any way can mark the signature as no longer valid, so keep the original of anything you've signed digitally.
What does "Maximum" do differently?
Maximum turns every page into a compact image. That's very effective for scanned documents and image-heavy PDFs, but the text can no longer be selected, searched or read aloud by screen readers. Use it only when the other levels don't get the file small enough.