pdf-io

Compress a PDF

Make a PDF smaller for email and upload limits. The file is compressed on your device and never uploaded.

How to compress a PDF

  1. Drop your PDF into the box above, or choose it from your device.
  2. Pick a quality: Smallest, Balanced or High quality.
  3. Select Compress PDF and wait while your device does the work.
  4. Download the smaller file. If compression would make it bigger, PDF-IO tells you to keep the original.

What compression changes

PDF-IO rewrites your PDF with Ghostscript's pdfwrite device. Embedded images are downsampled to the resolution you chose, fonts are subset to the characters you use, and duplicate resources are merged. Text stays text, so it remains searchable and sharp.

Prefer the command line?

The same result on Linux or macOS with Ghostscript installed:

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile=out.pdf in.pdf

Questions

Is my PDF uploaded when I compress it?
No. PDF-IO runs Ghostscript, compiled to WebAssembly, inside your browser. The PDF is read and compressed on your device, and nothing about the file is sent to a server.
How much smaller will my PDF get?
It depends on the content. PDFs with photos or scans often shrink by 50 to 90 percent. PDFs that are mostly text are usually already small and may not shrink much.
Which quality setting should I choose?
Balanced (150 dpi images) suits email and online forms. Smallest (72 dpi) is for viewing on screens only. High quality (300 dpi) keeps images sharp enough for printing.
Can I compress a password-protected PDF?
Not directly. Remove the password first in a PDF reader that knows it, then compress the unprotected copy.
Is there a file size limit?
There is no fixed limit, but very large PDFs (several hundred megabytes) depend on your device memory. Compression stops after 5 minutes.
Does it work on a phone?
Yes. PDF-IO works in current browsers on iPhone, iPad and Android as well as on computers.

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