Compress PDF Files — Private, No Upload
Reduce the file size of your PDF while maintaining the best possible quality.
How to compress a PDF — 3 steps
- 1
Add your PDF
Drop the file into the box above. Large files are fine — compression happens on your device, so there is no upload limit imposed by a server.
- 2
Choose a compression level
Pick the balance between file size and visual quality. Stronger compression re-encodes images at a lower quality; lighter settings keep documents crisp.
- 3
Download the smaller file
Save the compressed PDF to your device and check the result. If it is still too large, run it again with a stronger setting.
Why PDFs get big — and what compression actually does
Most oversized PDFs are heavy because of images: scanned pages, embedded photos, or screenshots stored at print resolution. Compression reduces size mainly by re-encoding and downsampling those images to a resolution appropriate for screens, while leaving the text itself sharp — text in a PDF is stored as vector data and costs almost nothing.
Typical results depend on the document. Scanned files and image-heavy presentations often shrink by 50–90%, while a text-only PDF that is already efficient may barely change. If your file needs to fit under a specific cap — Gmail and Outlook attachments allow 25MB and 20MB, and many application portals allow far less — compress, check the size, and repeat with a stronger level if needed.
Compressing locally has a practical advantage beyond privacy: there is no double transfer. Server-based compressors make you upload the full-size file and download the result, which for a 100MB scan can take longer than the compression itself. Here the file never crosses the network at all.
Your files never leave your device
Your document is compressed in your browser's memory — the original and the compressed copy both stay on your device from start to finish.
Most online PDF sites upload your document to their servers, process it there, and keep a copy for minutes, hours, or longer. PilotPDF works differently: the page downloads a small processing engine into your browser, and your file is opened and edited in your device's memory using WebAssembly. Nothing is transmitted, so there is nothing for a server to store, leak, or scan. You can even disconnect from the internet after the page loads and the tool keeps working.
Read more about how this works in our privacy-by-design explainer.