Compress PDF: how it works
To compress a PDF, open the Compress PDF tool, add your file, and PDFER reduces its size by optimizing and re-encoding images in your browser, then lets you download the smaller PDF. The file is never uploaded, so even large or confidential documents stay private.
How to use Compress PDF
- Open the Compress PDF tool and add your PDF.
- Let PDFER optimize and re-encode the file locally.
- Download the smaller PDF.
In your browser vs. uploading to a server
Best for shrinking a PDF to fit an email attachment limit (often 25 MB) without uploading it. Compression trades some image resolution for a smaller file; text stays sharp.
Frequently asked questions
How can I reduce PDF file size for free?
- Open the Compress tool and add your PDF; PDFER re-encodes images to cut the file size and downloads the result. It is free and runs in your browser.
Will compressing reduce quality?
- Compression mainly lowers embedded image resolution, so photos become smaller and slightly softer while text remains crisp. It is ideal for sharing and email.
Are my files uploaded to a server?
- No. PDFER runs entirely in your browser using WebAssembly and JavaScript. Your files are read into memory on your device, processed locally, and never sent to PDFER or any third party. Closing the tab or leaving the tool erases them from memory.
PDFER is a privacy-first PDF toolkit built by Kiril Urbonas. Every tool runs entirely in your browser — see our security model and privacy policy.