Compress PDF
Shrink a PDF for email or upload. Runs in your browser.
Tip: this release uses lossless compression only. Image-heavy scans will shrink more once we ship the "rasterize" option in the next update.
Compress PDFs for real submission limits
Use Compress PDF when files are too large for email, school portals, or job applications. CalmPDF runs locally in your browser, so the original document stays on your device while you generate a smaller copy for sharing.
Need a workflow tuned for attachments and inbox limits? Follow our practical PDF email compression guide for file-size targets, quality tradeoffs, and quick checks before sending.
Private by design. Files stay on your device and are processed in-browser. No uploads, no account, no server-side storage.
Upload & controls
- Choose one PDF file to compress.
- Start compression and wait for local browser processing.
- Download the optimized PDF file.
How it works
- 1Drop your PDF into the box above — no upload required.
- 2Click Compress PDF and wait for the lossless optimization to finish in your browser.
- 3Download the compressed PDF. The original stays untouched.
Best for
- Meeting strict upload limits on portals and government forms.
- Sending scan-heavy files by email without bounce-backs.
- Reducing storage usage for shared document archives.
Not ideal for
- Current compression is lossless, so size reductions vary by file.
- Image-heavy scanned documents may only shrink modestly.
- No quality slider is available in this MVP.
Troubleshooting
- If compression appears stuck, refresh and retry with fewer open tabs.
- If the reduction is small, the PDF may already be optimized.
- If your device is low on memory, try the file on desktop.
Frequently asked questions
Is my PDF uploaded to a server?+
No. CalmPDF processes your file entirely inside your web browser using JavaScript. Your PDF never leaves your device.
How much can CalmPDF compress a PDF?+
Results vary by file. Text-only PDFs may shrink slightly, while image-heavy scans often need future lossy controls for major reductions.
Is there a file-size limit?+
The limit depends on your browser and device memory. Most laptops comfortably handle PDFs up to 200 MB.
Does compression reduce quality?+
Current compression is lossless, so page visuals stay the same while metadata and object streams are optimized.
Is CalmPDF free?+
Yes. All core PDF tools are free and unlimited, supported by unobtrusive ads.
Related guides
Practical walkthroughs to help you finish this workflow faster.
How-to
How to Compress a PDF on Windows
Step-by-step instructions for this PDF task, including common pitfalls to avoid.
Read guideHow-to
How to Compress a PDF on Mac
Step-by-step instructions for this PDF task, including common pitfalls to avoid.
Read guideHow-to
How to Rotate a PDF
Step-by-step instructions for this PDF task, including common pitfalls to avoid.
Read guideRelated PDF tools
Continue with the next PDF action using these related browser-based tools.
Edit PDF
Add text, images, signatures, and initials in your browser.
Rotate PDF
Rotate all pages in a PDF in your browser. Fast and private.
Merge PDF
Combine two or more PDFs into a single file. Private and fast.
Split PDF
Extract a range of pages or split one PDF into many.
Extract PDF pages
Select specific pages and export a new PDF in your browser.
Reorder PDF pages
Move PDF pages into the exact order you need, directly in your browser.
Word to PDF
Turn a Word document into a PDF in your browser.
PDF to JPG
Convert every PDF page into JPG images locally in your browser.
PDF to Word
Convert simple PDFs into editable Word documents (.docx).