Nothing is uploaded. When you choose or drop a PDF, the browser File API reads it into memory, pdf.js renders each page to an image you can place signatures on, and when you press Sign & Download pdf-lib embeds your signature images into the pages and writes a new PDF, all on your own machine. The signed file is handed back from a local Blob for download; no bytes are sent anywhere. That matters because the documents people sign — contracts, offer letters, NDAs, leases, consent and tax forms — are exactly the papers you would not want to hand to a cloud service. There is no login, tracking or CDN in the processing path, the tool works offline once cached, and closing the tab discards everything. Signatures you draw are only ever stored in your own browser’s local storage for reuse, never transmitted.

The signature this tool creates is an electronic signature: a visual mark drawn, typed or uploaded and composited onto the page. Under the U.S. ESIGN Act and UETA, and the EU’s eIDAS regulation, a contract or signature cannot be denied legal effect simply because it is electronic, so e-signed PDFs are broadly enforceable when the usual conditions are met — intent to sign, agreement to do business electronically, and each party keeping a copy of the record. What this is not is a certificate-based digital signature, which uses PKI cryptography to cryptographically bind a verified identity to the file and prove it has not been altered since signing. Some high-stakes or regulated documents (certain notarised deeds, wills, or filings that specifically demand a qualified/advanced digital signature) may require that cryptographic form or a dedicated e-signature service with audit trails. For everyday agreements a drawn or typed signature is normally fine; when in doubt, confirm the requirement for your specific document and jurisdiction.

When you tap Signature (or Initials), a panel opens with three modes. Draw gives you a canvas where you sign with a mouse, trackpad, finger or stylus, and you can pick a pen thickness and ink colour; the drawing is auto-cropped to your strokes so there is no empty box around it. Type lets you enter your name and renders it in one of eight cursive/handwriting fonts (Dancing Script, Great Vibes, Pacifico, Satisfy, Sacramento, Allura, Caveat, Homemade Apple) in your chosen colour. Upload lets you pick an existing image of your signature; a transparent PNG blends most cleanly onto the page. Whichever you choose, the signature is placed as a movable, resizable box — drag it anywhere, use the + / − buttons to size it, and add it to any page. You can also drop an initials mark and an automatically dated stamp, and signatures you draw are remembered locally so you can reuse them with one tap.

Sign PDF is completely free with no sign-up, watermark or limit, and because it is 100% client-side it works in any modern browser on Android, iPhone, iPad, Windows, macOS or Linux with no app to install — touch drawing and dragging are fully supported. Multi-page documents show page navigation buttons and a thumbnail strip (with a badge counting the marks on each page), so you can place a signature, initials or date on whichever pages need them. When you press Sign & Download, the tool composites every placed element into the PDF at the exact position and size you set and downloads a normal, universally readable PDF as your original file name with a -signed.pdf suffix. One PDF is processed at a time and the whole file is held in browser memory, so a very large document is bounded by your device’s RAM.