Email gateways bounce oversized attachments, upload forms cap the megabytes, and a bloated PDF is slow to send and store. The Compress PDF tool re-saves your document with an optimised internal structure — packing its objects more efficiently and stripping redundant overhead — to bring the file size down so it sails through size limits.
How to use the Compress PDF tool
- Upload the PDF you want to shrink.
- Click Compress and let the tool rebuild the file.
- Compare the original and compressed sizes shown on screen.
- Download the optimised PDF.
What compression can and cannot do
It helps to understand where the savings come from. PDFs created by office software or assembled from many sources often carry duplicated and inefficiently stored data; rebuilding them with object streams can cut that waste noticeably. On the other hand, a PDF that is essentially a stack of high-resolution photographs is already dominated by image data, so it will compress less. Setting that expectation up front saves disappointment — text-heavy and "saved a dozen times" files shrink the most.
Tips to get smaller files
- Remove unneeded pages first; fewer pages always means a smaller file.
- Down-scale large images before building the PDF if photos are the bulk of the size.
- Run merged documents through compression, as combining files often leaves redundant data behind.
- Compare the numbers the tool reports to decide whether the saving is worth it.
The rebuild is handled locally by pdf-lib, so your document is optimised entirely on your device with no upload, no account and no watermark added to the result.
Quick reference
| Property | Detail |
|---|---|
| Input | One PDF |
| Method | Object-stream re-save |
| Best results | Text / redundant PDFs |
| Output | Smaller PDF + size report |
| Processing | In-browser |