Compress Scanned PDF
Shrink scanned PDFs in your browser: black & white, grayscale or colour, DPI choice and paper clean-up. Text pages stay untouched. Free and never uploaded.
- No upload — 100% private
- Instant, on your device
- Free, no sign-up
- Works offline once loaded
How it works
How to use Compress Scanned PDF
Drop your scanned PDF — every page is checked to see which ones are scans and which have real text.
Choose Colour, Grayscale or Black & white and a resolution (150 DPI suits most documents).
Keep “Whiten paper background” and “Remove dark scanner borders” on for cleaner, smaller pages, or set a target size in KB.
Click Compress scanned PDF, flip the preview between Before and After, then download.
Why use it
Why use our Compress Scanned PDF tool
Knows which pages are scans
Pages without a text layer are recompressed; pages with real text are kept exactly as they are, unless you choose to convert them too.
True black & white mode
Adaptive thresholding turns grey, shadowed scans into crisp 1-bit pages — often a tenth of the colour size.
Clean-up built in
Whitens yellowed or grey paper and paints out the dark edges flatbed scanners and phone photos leave behind.
DPI and quality control
Pick 100, 150, 200 or 300 DPI and a JPEG quality — or enter a target size and we search for the sharpest fit.
Same pages, same layout
Page sizes, rotation, links and page order are preserved exactly; only the scan images inside are replaced.
Private by design
IDs, contracts and medical letters are processed by your browser and never uploaded anywhere.
FAQ
Frequently asked questions
Why are scanned PDFs so much bigger than normal PDFs?
Each page of a scan is a full photo of the paper, often in colour at 300 DPI or more. A typed PDF stores the letters as text instead. Converting scans to black & white or grayscale at 150 DPI usually removes most of that weight.
Which mode should I choose?
Black & white gives the smallest files and the crispest look for printed or typed text. Grayscale keeps pencil, signatures and stamps natural. Colour is only worth it for photos, highlighter or coloured forms.
Will text in my PDF stay selectable?
Pages that already have real, selectable text are left untouched by default. Scanned pages never had selectable text — to get the words out of them, use an OCR tool such as Image to Text.
What DPI is best for scanned documents?
150 DPI is the sweet spot for reading on screen and normal printing. Use 200–300 DPI for small print or documents you will print and re-scan, and 100 DPI when the size limit is very strict.
Does it change my page size or orientation?
No. A4 stays A4, Letter stays Letter, and rotated pages keep their rotation. Only the image inside each scanned page is replaced with a smaller one.
Is it safe to compress confidential scans here?
Yes. Everything runs inside your browser on your own device. The PDF is never uploaded, and you can even disconnect from the internet once the page has loaded.
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