Do you know any tool for signing documents that assures privacy?

There are loads and loads of online tools for signing documents. From time to time I need to sign important things like employment contracts etc. but it's hard to find a tool that assures me the document I upload is not being saved, scanned or analyzed to get my personal data out of it.

Do you know of any such tool?

Edit: for clarification, I mean manual signing, like with a pen, on PDF or similar documents (not digital signing)