Use a browser-based PDF compressor that shrinks the file entirely on your own device, so the document is never sent to a server. It is free, needs no account, and works even offline once the page has loaded.
Most "free" online PDF compressors upload your file to their servers to process it, which is a real privacy problem when the document is a contract, a bank statement, an ID or a signed form. A client-side compressor loads a small library into your browser and does the whole job locally, so the file stays on your machine and nothing is stored anywhere.
The savings depend on what is inside the PDF. Scanned pages and image-heavy files usually shrink the most because the images can be re-encoded, while a PDF that is mostly text is already small and will change less. You can compress, check the result, and try again with no limit.
No. The compression runs entirely in your browser, so the file never leaves your device.
There is no account and no daily cap. Very large files are limited only by your device memory.
Yes, it runs in any modern mobile or desktop browser with nothing to install.