Sign PDF

about this tool

Not a digital signature

This tool draws a picture of a signature onto a PDF. It is not a cryptographic digital signature: nothing here binds a certificate to the file or makes later changes detectable, and the page says so above the save button. That kind of signature needs a certificate issued to you, which a web page cannot honestly provide. For everyday forms, a drawn signature is usually what is being asked for.

Three ways to sign

Draw with a mouse, trackpad or finger. The pointer positions are thinned out with the Ramer–Douglas–Peucker algorithm, which drops the samples that add nothing to the shape, and the rest are smoothed into a curve that runs through the midpoints between them — the usual way to get a clean line out of noisy input. The result is written into the PDF as a vector path, so it stays sharp at any zoom and costs a few hundred bytes. You can save the same strokes as an SVG.

Type a name in one of the PDF built-in italics. No handwriting font is shipped with this page, so a typed signature looks typed; the type size is fitted to the box, shrinking for a longer name rather than running past the edge.

Upload a PNG or JPEG photograph of your signature. The white-paper option makes near-white pixels transparent, so the ink sits on the page instead of in a white rectangle. It is a plain brightness threshold: a grey, shadowed or coloured scan will keep some of its background.

Placing it

The chosen page is drawn by pdf.js and the dashed box is dragged onto it, or nudged with the arrow keys once focused, with shift for bigger steps. The corner handle resizes it and the box keeps the signature's own shape, so nothing is stretched. The position is kept as fractions of the page, so it means the same thing whatever size the preview is, and the size in millimetres is shown as you drag. A page stored rotated — a scan, usually — is handled: the box lands where you see it and the signature is turned to match. An optional dated line is written underneath.

What is written

pdf-lib appends the signature to the content of each chosen page: a path for ink, text for a typed name, an embedded image for an upload. The rest of the document is untouched and the producer is set to this site. Because it is page content rather than an annotation, a viewer cannot select and delete it — and equally, nothing stops someone signing their own copy of the original.

Limits

Encrypted PDFs are refused, since they cannot be changed without the password. There is no certificate, no timestamp authority and no signature field: a PDF form's existing signature widget is ignored rather than filled. Everything runs in your browser and nothing is stored between visits, so a signature you draw is gone when you close the page unless you save the SVG.

To stamp every page rather than sign one, watermark & page numbers does that; to lock the file once signed, protect PDF adds a password.

questions

Is this a legally binding digital signature?

No, and the tool says so on the page. This draws a picture of a signature onto the document. A cryptographic digital signature binds a certificate to the file so that any later change is detectable; that needs a certificate authority and is not something a web page can do honestly. For many everyday forms a drawn signature is accepted, but it proves nothing on its own.

What does a drawn signature become in the file?

Real vector strokes. The pointer positions are simplified, smoothed into a curve through their midpoints and written as a PDF path, so the ink stays sharp at any zoom and adds a few hundred bytes rather than an image. You can also save it as an SVG to keep.

Can I use a photo of my signature?

Yes, as PNG or JPEG. The white-paper option makes near-white pixels transparent so the ink sits on the document rather than in a white box. It is a simple brightness threshold, so a grey or shadowed scan will keep some of its background.

How do I place it exactly?

Drag the dashed box on the page preview, or focus it and use the arrow keys, with shift for bigger steps. The corner handle resizes it, keeping the signature’s shape. The size in millimetres is shown as you go, and pages stored rotated are handled, so the box lands where you see it.

Can the signature be removed again?

It is drawn into the page content, so it cannot be selected and deleted in a viewer the way an annotation can. It is not protected either: anyone with the original file can produce their own version. Keep the signed copy if it matters.