Compress a PDF

Why some PDFs are huge and some are tiny

A PDF created from a Word document is mostly text and vector instructions and is usually a few hundred kilobytes, even for dozens of pages. A PDF created by a scanner or a phone camera is a stack of full-page photographs and can be 5 to 10 MB per page. The second kind is what fills inboxes and hits upload limits, and it is the kind this tool is built for.

How the compressor works

Each page is rendered to an image at a chosen resolution and re-encoded as a JPG at a chosen quality, then reassembled into a new PDF. That does three things at once: it lowers the pixel dimensions of over-sized scans, it applies efficient JPG compression to pages that were stored as uncompressed or lightly compressed images, and it strips embedded resources that are no longer needed. The compression level sets how aggressive both the resolution and the quality reduction are.

What you lose

Because pages are re-rendered as images, the output is a scan-style PDF: text is no longer selectable or searchable, links do not work and form fields are flattened. For a scan that was already just pictures of pages, nothing is lost. For a text-based PDF from Word or a design tool, compression is the wrong tool; those files are already small, and you would be trading a small, searchable file for a larger, non-searchable one. In that case the size is usually coming from a few oversized embedded images, and the fix is to re-export from the source application with image downsampling enabled.

Expected results

• A 20-page phone-scan PDF at 60 MB typically compresses to 3 to 6 MB at medium.
• A flatbed scan at 600 dpi drops by 80 to 90% at medium with no loss of legibility.
• A text-only PDF from Word may get bigger, not smaller. Do not compress those.

Reaching a specific size limit

Email attachments generally need to be under 10 to 25 MB, government and university portals often cap uploads at 2 to 5 MB, and some job application systems at 1 MB. Start with medium, check the result, and step up to strong if it is still too large. If strong is not enough, use the split tool to remove unnecessary pages first. Everything happens on your device, so bank statements, ID scans and medical documents stay private.