PDF Compressor — Free, Private, Browser-Based
Reduce PDF file size for email attachments, web uploads, or storage. Compression runs entirely in your browser using PDF.js — your documents never leave your device.
How to reduce PDF file size for email
- Drop your PDF. Drag and drop one PDF file into the upload area, or click to browse. Multi-page documents up to 500 pages work fine.
- Pick a compression preset. Choose Low (best quality, smallest reduction), Medium (balanced — recommended for email), or High (maximum compression, may visibly reduce image quality).
- Wait for processing. Compression runs in your browser. A 40 MB PDF typically processes in 15–45 seconds depending on your device.
- Download the compressed PDF. Click Download to save the smaller PDF. Original file is unchanged.
Use Cases
Frequently Asked Questions
Are my PDFs uploaded to a server?
No. Compression runs entirely in your browser. Your PDFs never leave your device.
How much can it shrink a PDF?
Typical reduction is 40–80% depending on content. PDFs with high-resolution images compress most; text-only PDFs compress less.
Does it work on password-protected PDFs?
No. Password-protected PDFs must be decrypted first. We recommend using a desktop tool for sensitive encrypted documents.
Is there a page limit?
No hard limit. Performance depends on your browser memory. We have tested 500-page PDFs successfully on modern devices.
Will text still be searchable?
Yes. Text remains selectable and searchable. Only image and font data is compressed.
Does compression add watermarks?
No. Output PDFs have no watermark, branding, or trial limitations.
Where PDF bloat actually comes from
A PDF is a container, not one file format — its size almost never comes from the text layer (vector text is tiny) but from embedded raster images: scanned pages, screenshots, or photos placed at print resolution (300 DPI) when the document is only ever viewed on screen. Compression works by re-processing those embedded images, not the text.
| Preset | What it changes | Typical reduction | Best for |
|---|---|---|---|
| Low | Re-encodes images at ~90% JPEG quality, keeps DPI | 10–30% | Documents with diagrams/charts where sharpness matters |
| Medium | Downsamples images to ~150 DPI + 75% JPEG quality | 40–70% | Email attachments, most scanned documents (recommended default) |
| High | Downsamples to ~96–110 DPI + 50% JPEG quality | 60–85% | Multi-page scans where file size matters more than image crispness |
- A scanned 20-page document at 300 DPI can easily hit 40 MB because each page is effectively a full-resolution photo; the same pages at 150 DPI (still perfectly legible on a screen) often come in under 5 MB.
- Fonts get subsetted too (only the glyphs actually used are kept), which matters for PDFs with embedded custom fonts but adds little compared to the image downsampling step.
Related tools
More free, in-browser tools from the Documents & Utility set — every one runs locally, with no sign-up and no upload.