Key takeaways
- Images make PDFs big; text and vector graphics are tiny.
- Good compression only optimizes images, so text stays crisp and searchable.
- Recommended is the best balance; Extreme for strict upload limits; Less for printing.
- Scanned PDFs often shrink by 50–90%.
A PDF that's too big bounces from email, fails on upload portals and fills your phone. Compression fixes that — and done right, you won't see a difference.
What makes a PDF big?
Almost always: images. A scanned page is a high-resolution photo, often 1–3 MB. Text, by contrast, takes a few kilobytes per page. So a 20-page scan can be 30 MB, while a 200-page text report is 1 MB.
How smart compression works
Compress PDF leaves text and vector graphics untouched — they stay razor-sharp and searchable. It only resamples and re-encodes images to a sensible resolution for their size on the page.
Choose the right level
| Level | Image quality | Use it for |
|---|---|---|
| Less | High (near original) | Printing, documents with photos |
| Recommended | ~150 dpi, very good | Email, sharing, most uploads |
| Extreme | ~110 dpi, smallest | Strict size limits, archiving many scans |
How to compress a PDF
- Open Compress PDF.
- Add one or more PDFs.
- Choose Recommended (or another level).
- Download the smaller file and check that small print is still readable.
Compress at the source
If you're scanning, you can avoid big files from the start:
- Pick Standard quality instead of High when saving.
- Use Grayscale or Black & white for text documents.
Typical results
- Phone scans: 50–90% smaller
- PDFs with photos: 30–70% smaller
- Text-only PDFs: little change (already small)
Common reasons to compress
- Email attachment limits (often 10–25 MB) — see reduce PDF size for email
- Government and university portals (often 1–5 MB)
- Saving phone and cloud storage
Your files stay private
Compression runs in your browser. Contracts, bank statements and medical records never leave your device.
Frequently asked questions
Will compression make my text blurry?
No. Text and vector graphics are kept as they are; only images are optimized.
Why didn't my PDF get smaller?
If it's mostly text and vectors, it's already compact. Compression helps most with scans and photos.
Can I compress a password-protected PDF?
Unlock it first with Unlock PDF (you need the password), then compress.
What level should I use for printing?
Less keeps images near their original quality while still reducing size.