Are Online PDF Tools Safe? How to Check
How most PDF sites work
Most free PDF sites upload your document to their server, process it there and send back the result. Your contract, tax form or ID scan then sits on someone else's computer, at least for a while, under a privacy policy you probably did not read.
A different approach
76 PDF does the work inside your browser using open source code. Your file is read into your own device's memory and the result is saved straight back. There is no upload step, because there is no server that could receive it.
How you can verify it
Open your browser's developer tools, go to the Network tab, and use any tool. You will see no request carrying your file. You can also install the app and turn off your internet connection: the tools still work, which would be impossible if they needed a server.
What does leave your device
The contact form sends the name, email and message you type through the Web3Forms service so we receive it by email. Nothing else is sent.
Good habits regardless of the tool
Prefer tools that work offline, use HTTPS, publish a clear privacy policy and do not ask you to sign up. Keep sensitive files off public computers, and password protect anything confidential before you share it.