How to get a PDF under 500 KB
- Tap Choose your document and pick the PDF, however many pages it runs to.
- The target is already 500 KB. Tap Compress to 500 KB.
- Let it run — a twenty-page scan takes a little while on a phone.
- Check the size it reached, then save the smaller copy.
A long scan is the easiest thing to shrink
A twenty-page phone scan is twenty full-page photographs, and photographs are exactly what this tool re-encodes. Files like that routinely lose most of their weight without any visible harm, because a phone camera captures far more detail than a printed page contains and the surplus is pure cost. Five hundred kilobytes across twenty pages is twenty-five each, which is comfortable for typed text.
Each page is worked on separately and keeps whichever version came out smaller, the new one or the one it already had. That stops an already tiny page — a blank sheet, a simple line drawing — from growing while the rest of the document shrinks.
The parts of your file it will not touch
Some things inside a PDF are left alone deliberately. Transparency masks are skipped, because an artefact in that channel shows up as a visible halo around a logo. Images stored in the fax format that black-and-white scanners produce are skipped, because re-encoding them as photographs makes them bigger. Anything the browser cannot decode safely is copied across byte for byte instead of guessed at.
Each of those is reported when the job finishes, so a file that shrank less than you expected arrives with its reason attached, rather than leaving you wondering whether you pressed the wrong button.