Compress PDF

Email, school portals and job sites often cap uploads at a few megabytes, and scanned or photo-heavy PDFs blow past that. This compressor shrinks PDFs in your browser — the files never leave your device — with three levels, from a lossless clean-up that changes nothing visible to a strong mode that rebuilds every page as a compact image.

How to use this tool

1. Choose one or more PDF files.
2. Pick a level: Light for a lossless clean-up, Recommended to recompress photos and scans, or Strong when the file must be as small as possible.
3. For Recommended and Strong, set the image quality (60–75% suits most documents) and the maximum resolution; 150 DPI suits screens and office printers.
4. Download the compressed file, or all of them as a ZIP. If no smaller version is possible, the original is kept.

Formula

Reduction = (1 − compressed size ÷ original size) × 100%. Recommended mode limits each image to (long edge of its page in inches) × DPI pixels on its long side, then re-encodes it as JPEG at the chosen quality.

An A4 page is 11.69 in on its long edge, so at 150 DPI an image on it keeps at most 11.69 × 150 ≈ 1,754 px on its longest side. A recompressed image is only used when it is at least 5% smaller than the original.

Example

A 12-page scanned contract of 18.4 MB holds twelve 300-DPI colour scans. With Recommended, 150 DPI and 70% quality each scan is halved in both directions and re-encoded; the file typically drops to about 2–3 MB, roughly 85% smaller, and stays sharp enough to read and print.

What each level changes

Light removes unused objects, thumbnails and editor data and compresses the file structure; text, vectors and images are untouched. Recommended also re-encodes photos and scans. Strong renders each page to a JPEG: it shrinks scans the most, but text becomes unselectable and links and form fields are dropped. Files that are mostly text and vector drawings are often already compact — then the original is kept.