Signing without sending your contract anywhere
Signing a document online normally means uploading it. You hand a company your lease, your employment contract, or your NDA, along with an image of your signature, and trust their retention policy. For a routine form that may be fine. For anything sensitive it is a strange trade to make for what is, technically, a very small operation.
Here the whole thing happens in the tab. The PDF is read into memory, the page is rendered so you can see where you are placing things, your signature is drawn onto a canvas, and pdf-lib embeds it into the document — all locally. Nothing is transmitted, so there is nothing stored, logged, or subpoenable afterwards.
Drawn or typed
Drawing gives you your actual signature, and works best with a finger on a phone or a stylus on a tablet — a mouse produces something that looks like a mouse drew it. The stroke is captured with pointer events, so it stays continuous even if your flourish overshoots the edge of the pad.
Typing renders your name in a script face. It looks less personal but it is crisp at any size, which matters if the signature has to be large. Both paths produce the same thing: a PNG with a transparent background, trimmed to its ink, so nothing stamps a white box over the page underneath.
What this is, legally
Worth being precise about, because the word “signature” covers two quite different things.
What this produces is a simple electronic signature. Under the US ESIGN Act, the EU's eIDAS regulation, and equivalent legislation elsewhere, an electronic mark made with intent to sign is generally valid for ordinary commercial agreements, and courts have upheld far less than a drawn signature — including typed names in emails.
What it is not is a digital signature. That term means something specific: a cryptographic hash of the document, signed with a private key whose certificate was issued by a trusted authority. It proves both who signed and that nothing has changed since. It also requires a certificate you have to obtain from a certificate authority, which no web page can hand you.
The practical rule: for a rental agreement, a permission slip, an invoice approval, or an NDA, this is almost certainly sufficient. For a property deed, a will, anything requiring notarisation, or anything where a counterparty may later dispute that they signed, get proper certificate-based signing.
How placement works
The page preview is rendered at screen resolution by pdf.js, and your placement is recorded as fractions of the page rather than pixels. That is what makes the position accurate regardless of the preview's scale — a signature you drop two-thirds across a 600-pixel preview lands two-thirds across the real page, whether that page is A4 or tabloid.
The signature is stamped as an ordinary image object on top of the existing content. Nothing underneath is disturbed, the text stays selectable, and the rest of the document is byte-for-byte what it was.
Common uses
- Signing a rental or employment agreement without printing it
- Returning a countersigned invoice or purchase order
- Adding initials to each page of an agreement
- Signing a permission slip or consent form on a phone
- Approving a document that would otherwise need a scanner