The hidden upload
Every “upload your PDF” tool moves your document to a server you don’t control. Even with good intentions, that server can be logged, breached, or subpoenaed. The safest document is one that never leaves your device.
What “local processing” actually means
Browser-based tools run the conversion code in your tab. The file is loaded with the File API, processed by JavaScript and WebAssembly, and saved back out — with no network request carrying your content.
How to verify it
Open your browser’s network tab while you use the tool. With PDFIntro you’ll see the libraries load once, then silence while you work. No request carries your file because there’s nowhere for it to go.
The trade-offs
Local processing uses your device’s memory and CPU, so extremely large jobs can be heavier than a server farm. For the vast majority of documents, though, it’s both faster and far more private.
