Most "free online PDF converter" sites work the same way: you upload your file, their server processes it, and they send a PDF back. For a grocery list that's fine. For a contract, a medical form, or a résumé with your address and phone number, it's worth a second thought.
What "upload" actually means
When a document leaves your device, it sits — however briefly — on a computer you don't control. You're trusting that company's retention policy, security, and honesty. Most are fine. But you can't verify any of it, and a document you can't un-send is a document you no longer fully control.
The client-side alternative
In-browser conversion flips the model. The code that reads your Word file and builds the PDF runs inside your own browser tab, on your own device. The file is loaded into memory locally and never transmitted anywhere. There's no server copy because there was never an upload.
- Nothing to leak: the document doesn't exist on anyone else's machine.
- Nothing to retain: close the tab and the file is gone from memory.
- Nothing to recover: which also means no one, including us, could hand it over.
How to tell which kind you're using
A quick signal: try converting with your Wi-Fi and data turned off after the page has loaded. A client-side tool keeps working; a server-based one fails, because it needed to send your file away. docx2pdf.app keeps working — by design.
Privacy isn't only about hiding something. It's about not handing copies of your documents to strangers when you don't have to.