Compress a scanned PDF

A scanned PDF is a stack of photos of pages, which is why a ten-page scan can be bigger than a 300-page ebook. The Recommended setting is selected: it scales each page image to a sensible resolution and saves it as an efficient JPEG, which usually cuts colour and greyscale scans to a fraction of their size with the text still clear.

How to use Compress a scanned PDF

  1. Choose the scanned PDF, whether it came from an office scanner, a printer's scan-to-email or a phone scanning app.
  2. Keep Recommended for a good balance, or pick Target size if a form gives you an exact limit.
  3. Download and zoom in on the smallest print, such as stamps and signatures, to check it is still legible before you submit it.

Frequently asked questions

Why are scanned PDFs so large?

Scanners often save every page as a high-resolution colour image, even when the page is black text on white paper. Each page can be several megabytes, and most of that detail is not needed to read the page on screen or print it again.

My scan hardly shrank. Why?

Some scanners already save black-and-white pages with fax-style or JBIG2 compression, which is very compact. Those pages are left as they are, so there is little to gain. Colour and greyscale scans shrink the most.

Can I search or copy the text after compressing?

Only if the scan already had a text layer from OCR, which compression keeps. If not, run the file through OCR PDF to make the text searchable and copyable.

Should I scan in colour or greyscale?

Greyscale for text documents, and colour only when colour matters, such as stamps, photos or highlighted forms. A greyscale scan is smaller before compression even starts.

Is my file uploaded?

Your file is processed in your browser and is never uploaded to our servers.

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