Compress PDF

About the Compress PDF tool

Compress PDF reduces file size by rendering each page to a canvas via pdf.js and re-encoding it as an optimized JPEG at a quality level you choose, then rebuilding a new PDF from those images with jsPDF — all inside your browser tab. This is especially effective on scanned documents and image-heavy PDFs, where the original file size usually comes from high-resolution photos or scans rather than the text itself.

Large PDFs cause real, everyday friction: an email bounces because the attachment is over a provider's limit, a form submission portal rejects a file for being too big, or a shared drive fills up faster than expected. Compress PDF exists to solve exactly that — get a file that fits, without switching to a different tool or emailing yourself a lower-resolution scan.

Why rasterizing shrinks the file so much

Most oversized PDFs are large because of embedded images stored at a far higher resolution than needed for on-screen reading — a page scanned at 600 DPI, for example, contains roughly four times the pixel data of the same page at 300 DPI, for no visible benefit on a laptop screen. By rendering each page at a controlled scale and re-encoding it as a JPEG at a sensible quality setting, this tool throws away that invisible excess detail while keeping everything a reader actually sees intact.

One honest trade-off worth understanding: this technique converts each page into a flattened image, the same as a scan, which means any text that was previously selectable and searchable in the original will no longer be. If preserving selectable text matters more than file size, the Light setting uses the highest render quality and is the least aggressive option — but it still rasterizes, so keep your original PDF if you need it.

Choosing a compression level

Each level trades off render scale and JPEG quality differently. Light renders at a high internal scale with high JPEG quality — pick this for documents with small text or fine line art you want to stay crisp. Recommended is the default balance most people should start with. Maximum renders at a lower scale with more aggressive JPEG compression, ideal for scans and photo-heavy files where the smallest possible size matters most.

Compress PDF: this tool vs. the alternatives

Tips for the best results

• Always keep your original PDF — compression is a one-way trip once text becomes an image.
• Start with Recommended and only move to Maximum if the file is still too large for your purpose.
• Compressing a merged file? Run Merge PDF first, then compress the combined result once.
• Only need certain pages compressed? Use Split PDF to isolate them first.