Signing PDFs Online: What Happens to Your Signature After You Click Submit
Published 9 July 2026 · 5 min read
A signature is one of the few things that's genuinely, uniquely yours — it's on your lease, your loan paperwork, your employment contract, probably a dozen documents you don't remember signing. So it's a little strange how casually people upload it to random websites: draw it once in a free "sign PDF" tool, and that image of your signature, plus whatever contract you attached it to, both get sent off to a server to be combined.
Two things travel together, not one
It's worth separating what's actually at stake here, because it's two things, not one. There's the document itself — often a contract, lease, or agreement with real legal weight. And there's your signature, which functions almost like a piece of identity once it's captured as a clean digital image. Neither one is something you'd want floating around indefinitely, and a typical online signing tool asks for both, uploaded together, at the same time.
Once that signature exists as a digital file, it can, in principle, be dropped onto other documents too — which is exactly why it's not something to be careless about handing to a site you're using for the first time.
How this works differently here
FormatDog's Sign PDF tool lets you draw, type, or upload your signature, and stamps it onto the document using pdf-lib, entirely inside your browser. The document and your signature image are combined locally, in your browser's memory, and the result is generated on your own device. Neither the contract nor your signature is ever sent to a server to be processed.
Practically, that also means your signature isn't sitting in some company's storage after you're done using the tool. Once you close the tab, there's nothing left anywhere except the final signed PDF you downloaded.
How to check this on any signing tool
Open your browser's developer tools (F12), click the Network tab, then draw a signature and apply it to a document. If the tool uploads anything, you'll see a request carrying that data appear while it processes. If the tab stays quiet, the signing happened locally and nothing was sent anywhere.
A reasonable point in the other direction
Plenty of established e-signature platforms take real security seriously, and for business workflows that need audit trails, identity verification, or legal certification of who signed what and when, a proper e-signature service with those features is genuinely the right tool, not a local one. This is really about the simpler, everyday case: quickly signing a personal document without wanting your signature and a contract to make a round trip through a server neither needed to visit.