PDF Signature Adder
Research tool
PDF Signature Adder signs a PDF you already have, on an iPad or a laptop. You open the PDF, draw a signature with an Apple Pencil, a finger or the mouse, or paste or open a picture of one, tap the page where it goes, and save a signed copy. On an iPad the copy goes to Files, or to Mail or AirDrop through Share.
The PDF and the signature stay in the browser tab. The page loads once from GitHub Pages and then makes no further request, and it keeps nothing after the tab is closed. Its browser check fails if the page sends a request after it is ready or leaves anything in browser storage, and a script plants five leaks to show the check catches each one.
The signed copy is the original file, byte for byte, with the signatures appended as an incremental update, the way Acrobat and Preview add annotations. Text stays selectable, and links and form fields are untouched. A drawn signature is written as vector paths; a picture is written as an image with a transparency mask. The signature is a picture of handwriting, not a cryptographic digital signature, and it certifies nothing. The tool refuses a PDF it cannot amend safely and says why: one that is encrypted or locked against editing, one certified against any change, or one too damaged to read.
The rules (reading the PDF, where a signature sits on a rotated or cropped page, smoothing strokes, writing the update) run in a Rust core compiled to WebAssembly, and a vendored copy of pdf.js paints the pages. It is a Builder project.
Using the tool
Select Open PDF and choose the file. Select Add signature, then draw on the pad, or switch to Paste or Open image for a picture of a signature you already have. Select Use this signature and tap the page where it goes: its bottom edge lands where you tap, so a tap on a signature line puts it on the line. Drag it to move it, drag a corner to resize it, then select Save PDF and choose Download or Share.