How to compress a PDF
- Add one or more PDFs.
- Pick a level. Recommended suits most scans. Choose Light for photos and charts that must stay sharp, or Strong when you need the smallest possible file.
- Click Compress PDF and compare the size before and after.
How the compression works
Each page is redrawn as an optimised image at the resolution you choose (150, 110 or 72 dpi) and saved with efficient JPEG compression. This works best on scanned documents and image-heavy PDFs, which are usually the large ones, and can cut their size by 50–90%.
Because pages become images, the text can no longer be selected or searched. Keep your original if you need to copy text, and use the compressed copy for emailing and uploading. If a file cannot be made smaller, PDF Free gives you back the original instead of a bigger one.
Example: a scanned ID and bank statement
A phone scan of 6 pages is 18 MB, but the upload form allows 5 MB. With the Recommended level the file drops to about 2–3 MB, still easy to read on screen and in print.
Which level should I choose?
| Level | Resolution | Best for |
|---|---|---|
| Light | 150 dpi | Printing, photos, small text |
| Recommended | 110 dpi | Email, forms, everyday scans |
| Strong | 72 dpi | Strict upload limits, screen viewing |
Tips to get even smaller files
- Remove pages you do not need with Split PDF before compressing.
- Scan in greyscale rather than colour for text documents.
- Do not compress twice: each pass lowers quality a little more.
- Read our guide: how to reduce PDF file size.
Frequently asked questions
Why did my PDF not get smaller?
PDFs made of plain text (exported from Word, for example) are already small and efficient. Compression helps most with scans and photos.
Is my file uploaded?
No. All processing happens in your browser, using the open-source pdf.js and pdf-lib libraries.
Can I still print the compressed PDF?
Yes. The Light and Recommended levels print clearly on standard office printers.
Can I compress several PDFs at once?
Yes. Add them all; you can download each one or all of them as a ZIP.
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Last reviewed: 2026-11-08. Tools are provided as-is. Keep a copy of important originals. See our disclaimer.