How to Reduce PDF File Size
Learn why PDFs get large and how to compress one to fit an email or upload limit — what actually shrinks a file and the trade-offs to know.
By the ToolsHub team · Updated May 1, 2026
A PDF that won't attach to an email or fit an upload limit is almost always large because of images — usually scanned pages or photos embedded at full resolution. Compressing the PDF re-renders those pages at a lower resolution and quality, which can cut the file size several times over. Our free Compress PDF tool does this in your browser and shows the before-and-after size.
What actually makes a PDF smaller
- Downsampling images — the biggest win for scans and photo-heavy files.
- Lower JPEG quality — trades a little visual sharpness for a lot of size.
- Removing unused fonts and metadata — a minor gain by comparison.
The trade-off to understand
Compression that re-renders pages turns text into part of an image, so it's no longer selectable or searchable. That's a great deal for a scanned document, but for a text-based PDF it can even make the file larger — the tool warns you when that's the case. Keep your original either way.
An alternative for sharing single pages
If you only need to send a page or two as pictures — for a chat or a slide — converting with PDF to JPG is often smaller and simpler than compressing the whole document.