Compress a PDF - Choose Quality or Smaller Size
Choose a lighter structural optimisation or a stronger image-based reduction, then compare the result before downloading.
How to compress a PDF - 3 steps
- 1
Upload the PDF
Add one PDF up to 500 MB. The file is read in your browser before you choose the compression mode.
- 2
Pick a compression mode
Use Recommended to optimise the PDF structure without rasterising pages, or Extreme when making the file smaller matters more than keeping the best image quality.
- 3
Check and download
Compare the new file size and a few pages with the original, then download the result. If the source was already compact, the original may be kept instead.
What PDF compression changes
Images are usually the main reason a PDF is large. Scanned pages, phone photos, screenshots, and presentation graphics can contain far more image data than the document needs for its intended use. Compression targets that data first.
Recommended mode optimises the PDF structure without turning the pages into raster images. It is the sensible starting point for reports, forms, contracts, and documents that need to stay crisp. Text and vector drawings are handled differently from embedded images, so a text-heavy file may not become much smaller.
Extreme mode tries raster compression at several settings and keeps it only when it produces a smaller file. This can reduce an image-heavy scan more effectively, but the pages may lose detail or look softer when enlarged. The tool keeps the original if the attempted result would be larger.
Choosing between smaller size and better quality
For email, a web upload, or cloud storage, start with Recommended and check the resulting size. If the file still exceeds the service's limit, try Extreme and inspect small text, photographs, signatures, and diagrams before sending it.
For printing, use Recommended unless the document is too large to handle. A stronger setting can make scanned text, fine lines, or photographs less clear on paper even when the page looks fine at normal screen size.
A PDF that is already mostly text, vector artwork, or efficiently compressed images may show little or no reduction. That is normal; compressing it again cannot remove much without changing the content. Compare the original and the result instead of judging success only by the word 'compressed'.
What to check before sharing the smaller PDF
Open the downloaded file in a PDF reader and check the pages that matter most. Look at small type, charts, photos, signatures, forms, and any page with a dark background. Confirm that the file opens correctly and that its size is suitable for the destination.
Password-protected or encrypted PDFs may not open for compression. Unlock a file with a password you know first, then compress the unlocked copy. Keep the original document because compression creates a new file and is not a replacement for a backup.
Your files never leave your device
The PDF is compressed in your browser's memory. Your original file and the new copy stay on your device during the process.
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.