Compress PDF
Shrink your PDF file size online — free, fast, and with full control over quality and DPI. No sign-up needed.
- ✓ Free
- ✓ Quality slider
- ✓ DPI control
- ✓ No watermarks
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Why use PDF99?
Quality slider
Control exactly how aggressively images are re-encoded. High quality (85%+) gives minimal visible change. Lower values produce smaller files at the cost of some image sharpness.
DPI control
Set the target resolution for embedded images. 150 DPI is ideal for most digital uses. 72 DPI is optimal for web or email. 300 DPI retains near-print quality.
Real compression
When PDF.js is available, the tool re-renders each page at your chosen DPI and quality. This produces genuine file size reduction, not just metadata stripping.
No quality loss at high settings
Set quality to 85% or above and the output will be visually indistinguishable from the original.
Fast, local processing
Compression runs in your browser. Your PDF doesn't travel to a remote server.
No size limits
Compress any PDF regardless of how large it is.
What does compressing a PDF actually do?
PDF compression reduces file size by stripping unnecessary data and re-encoding content more efficiently. A PDF can accumulate extra bulk from embedded revision history, unused font glyphs, redundant objects, print settings, and embedded thumbnails — none of which are needed for viewing. Image-heavy PDFs compress further by re-rendering images at a lower resolution. The result is a smaller file that looks identical to the original at typical viewing sizes.
How to compress a PDF
Upload your PDF
Choose your PDF using the file picker or drag it onto the upload area.
Set quality and DPI
Adjust the quality slider and DPI to balance file size against image quality.
Download the result
Click Compress PDF and download your smaller file instantly.
Frequently asked questions
It depends on the content. Image-heavy PDFs compress well — often 30–70%. Text-only PDFs may shrink 10–20%. A PDF already optimised may barely change.
Quality controls how aggressively images are re-encoded (lower = smaller but blurrier). DPI controls the resolution of re-rendered pages (lower = smaller, less sharp).
No. Compress any PDF regardless of size.
Yes. Compression runs in your browser. Your PDF is not sent to a remote server.
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