Before using an online PDF tool with a sensitive document, find out whether the operation runs locally in your browser or sends file data to a service. Do not infer file handling from words like "private" or "secure" alone.
What local processing means
A browser-based operation runs its file-processing code on your device. The page may still load scripts, fonts, or model files over the network, so distinguish those resource requests from requests that contain your selected document.
Questions to check
- Does the specific tool page describe where processing happens?
Check the network behavior
For a non-sensitive test file, open the browser's developer tools and inspect the Network panel while using the tool. Look for requests made after selecting the file and review their destination and payload. A request can load a library or model without containing the document itself.
Before uploading sensitive files
If the tool's processing method is unclear, do not upload confidential, financial, medical, or identity documents. Check the tool page and privacy policy, or choose software whose handling practices you can verify.