Compress a PDF

Make a PDF smaller by re-encoding the images inside it, which is where nearly all the bytes of a large document are. Text, links and page structure are left exactly as they were.

Questions

Will it ever make my file bigger?

No. Re-encoding an already-optimised image often would, so the result is compared with the original and the original is kept whenever it is smaller. You are told when that happens rather than handed a pointless download.

How much smaller will my file get?

It depends entirely on how much of it is pictures. The page tells you before you start. A document that is 90% images has a great deal to give, and one that is 4% images has almost none.

Do my files get uploaded anywhere?

No. Every tool here runs inside your browser tab, on your own machine. The page also ships a Content-Security-Policy that blocks outbound requests entirely, so uploading is not something the app declines to do. It is something it cannot do. Click the "Private" badge to read the policy actually in force.