Compress a large scanned PDF
Office scanners and scanning apps often save every page at high resolution, so a ten-page scan can be tens of megabytes. That is mostly image data, which is exactly what compression reduces.
Compress PDF re-renders each page at the resolution (72, 150 or 300 DPI) and quality (Standard, High or Maximum) you choose. It runs in your browser, so scans of personal documents stay on your device.
For a scan of signed contracts, try 150 DPI and High quality, then compare the actual output size with your upload limit and inspect each signature. This is a starting point, not a promised size reduction: an already efficient scan may become larger after re-rendering.
Because pages are re-rendered, any text becomes part of the page image. For a scan that is already an image this changes nothing, but if you ran OCR to make the scan searchable, compress first and run OCR afterwards so the text layer is kept. 150 DPI is usually clear for printed text; use 300 DPI for small print or fine detail.
Step by step
- Open Compress PDF and add the scanned file.
- Choose 150 DPI and High quality as a starting point.
- Compress and compare the new size with the original.
- Zoom into small text; if it's blurry, try again at 300 DPI.
Tips
- Remove blank pages from the scan first with Delete PDF pages.
- Always compress from the original scan, not from an already compressed copy.
- Run PDF OCR after compressing if you need searchable text.
Questions
- How much smaller will it get?
- It depends on the scan; image-heavy scans usually shrink the most. The new size is shown before you download.
- Will text stay selectable?
- No. Pages are re-rendered as images, so run OCR afterwards if you need selectable text.
- Is my scan uploaded?
- No. Compression runs in your browser.
Related tools
Full guide: How to reduce PDF file size