How to Compress a Scanned PDF
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Scanned PDFs are the heavyweights of the document world. Every page is a full-resolution image, so a short scanned contract can outweigh a hundred-page text report. The flip side is the good news: because scans are nearly all image data, they compress more dramatically than any other kind of PDF — often by 70% or more.
This guide focuses specifically on compressing scans using the free Compress PDF tool, which runs in your browser with nothing uploaded. Scans are exactly the case where browser compression shines, and where the size savings are most worth having.
We'll also cover the one thing to watch with scanned documents — searchable text — so you don't accidentally lose a text layer you'd worked to create.
Step by step
- 1
Open the Compress PDF tool
Go to the Compress PDF tool in your browser. It processes the file on your device, so even a scanned contract stays private.
- 2
Add your scanned PDF
Drag the scan onto the drop zone or click to choose it. The tool reads it locally — nothing is uploaded.
- 3
Choose a level — you can go strong here
Scans tolerate strong compression well because they're images, not crisp vector text. Recommended often suffices; Strong can still look perfectly readable for everyday documents.
- 4
Compress and check readability
Run it and open the result. The key test for a scan is legibility — can you comfortably read the text? If yes at a strong level, take the bigger saving.
- 5
Mind the searchable text layer
If your scan was OCR-processed to be searchable, compressing it in the browser re-renders pages as images and removes that layer. Keep the searchable original if you need it.
- 6
Save the smaller copy
Save under a new name. Scanned files routinely drop well under email and upload limits in a single pass.
Tips
- Scans compress the best of any PDF — if a document is huge because it's scanned, you're in luck on the size front.
- Because scans are images, you can usually push to a stronger level than you'd dare with a designed document and still keep it readable.
- If your scan had a searchable text layer from OCR, browser compression removes it. Re-run text recognition afterwards, or keep the searchable original separately.
- Scanning at a lower resolution (200–300 DPI) at the source produces smaller files from the start, reducing how hard you have to compress later.
- Color scans are larger than grayscale. If color adds nothing to the document, scanning in grayscale shrinks it before compression even begins.
Try it on your phone
Scans usually start on a phone, and the PDF Editor app keeps the whole loop on-device: scan at a sensible quality, compress offline, and — unlike browser tools — run text recognition so the smaller file can still be searchable. No upload at any step.
