PDF Compression Guide: The Right Way to Shrink a PDF
What makes a PDF big, how much each setting saves and how to fit an email or upload limit.
What makes a PDF big?
A PDF's size is almost always decided by its images. A 10-page text-only document is usually a few hundred KB; if the same pages are scanned, each page is a photo and the file easily reaches 10–30 MB.
- Scanned pages and high-resolution photos (the biggest share)
- Embedded fonts (especially many different fonts)
- Repeated images, layers and leftovers from earlier edits
What does compression lose?
Text and vector drawings aren't affected by compression; they stay sharp. The saving comes from images, whose resolution and quality are lowered. 150 DPI is enough for documents read on screen; for print, don't go below 300 DPI.
Shrinking a scanned PDF
With scanned documents the biggest gains come from colour and resolution:
- Converting a black-and-white document to greyscale usually cuts the size by more than half.
- A 600 DPI scan can go down to 300, or to 150 for screen use.
- Removing blank pages and sending only the pages needed is the easiest win.
Order of steps to fit a limit
When a file is over a limit, go in this order: compress first; if that's not enough, split off unnecessary pages; if it's still too big, split the document into parts and send them separately. Official forms usually state the limit on the page; check it rather than guessing.
Recommended setting by purpose
Image resolution (DPI) is the setting that affects size the most. Suggestions for typical use:
| Purpose | Image resolution | Note |
|---|---|---|
| Reading on screen, email | 150 DPI | Text stays sharp, photos soften slightly |
| Official application (with a limit) | 150 DPI, greyscale | The biggest gain for scanned documents |
| Office printer | 200–300 DPI | Moderate saving without visible loss |
| Professional print | 300 DPI or more | Send as is rather than compressing |
| Archive | Original | Avoid lossy compression |
Tools for the job
Frequently Asked Questions
Does compressing a PDF blur the text?
No, real text and vector drawings aren't affected; only the images on the page shrink. On a scanned page the text is part of the image, so very aggressive compression can blur it.
How do I get a PDF under 1 MB?
Try the strongest compression first. For scanned documents, greyscale and 150 DPI are usually enough. If it's still too big, remove unnecessary pages or split the document.
Why don't some PDFs get smaller?
PDFs with only text and no images are already small and have nothing to compress. Files that were compressed before also gain little.
Can an encrypted PDF be compressed?
Remove the password first; then compress it and, if you like, protect it again.
Is my file sent to a server?
No. On Pixebag, PDF compression happens in your browser; the document never leaves your device.