It depends entirely on where your file goes. Here's what actually happens behind most "free online PDF" sites — and how to avoid the risk.
With most online PDF converters, clicking "upload" sends your document to the company's server, where it is processed and then offered back for download. During that round trip your file leaves your device and sits, however briefly, on someone else's computer. For a holiday photo that's fine. For a contract, payslip, bank statement, medical record or ID scan, it means a copy of sensitive data has travelled across the internet to a third party.
Some modern tools — including meldpdf — do all the work inside your browser using JavaScript and WebAssembly. Your file is read into the page's memory on your own device, processed there, and handed back as a download. It is never sent anywhere. There's no server that receives it, so there's nothing to retain, log or breach. That makes it appropriate for exactly the sensitive documents you shouldn't upload elsewhere.
You can confirm it yourself: load meldpdf, disconnect from the internet, and the tools still work.
Not necessarily — paid services often still process on their servers. "Where does the file go" matters more than "is it paid".
Usually it's faster, because there's no upload/download round trip — the work happens instantly on your device.
No. There is no meldpdf server that receives your documents. See our privacy policy.