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Most PDFs that need a signature fall into one of two jobs, and they call for different tools. The first is signing something that was sent to you: an NDA from a prospective client, a W-9 your accountant needs, a rental application, a school permission slip, a contractor's invoice you have to approve. You are the only signer, the document is already final, and you need it back in someone's inbox in the next few minutes. That is what this tool is for.

The second job is getting a signature from somebody else. The moment a second party is involved the questions change: who signed, when, from what IP address, in what order, and can you prove any of it six months later in a dispute? A signature stamped onto a page answers none of those. That is not a flaw in the tool — it is the difference between signing a document and running a signing process.

A useful rule of thumb: if you would be comfortable printing the document, signing it with a pen, and scanning it back, this free tool is a strictly better version of that workflow. If printing and scanning would not be good enough — because you need proof of identity, a defensible timestamp, or a record that survives your own word — you want a signing platform with an audit trail instead.

In the United States two laws govern this. The federal ESIGN Act of 2000 gives electronic signatures the same legal effect as handwritten ones for transactions in or affecting interstate commerce. The Uniform Electronic Transactions Act does the same at state level and has been adopted by 49 states; New York reached the same result through its own Electronic Signatures and Records Act. Both are deliberately technology-neutral — neither specifies a file format, an algorithm, or a vendor.

What they do require is four things. There must be intent to sign, the same standard applied to ink. There must be consent to do business electronically, which between commercial parties is usually implied by conduct. The signature must be attributable to the person who made it. And the resulting record has to be retainable and reproducible by everyone entitled to a copy. A signature you draw, burn into a PDF, and send back by email satisfies all four for the great majority of everyday agreements.

The European Union takes a tiered approach under eIDAS. A Simple Electronic Signature covers the drawn or typed variety and is admissible as evidence. An Advanced Electronic Signature adds a cryptographic link to the signer's identity and detects later tampering. A Qualified Electronic Signature, backed by a certificate from an accredited trust service provider, is the only tier that carries automatic legal equivalence to a handwritten signature across the EU. Most commercial contracts never need the qualified tier.

Where a simple signature genuinely falls short is evidence. It proves a mark is on the page; it does not prove who put it there. If a counterparty later denies signing, you are relying on the surrounding email trail. Some documents are also excluded from electronic signing in most jurisdictions regardless of the technology used — wills and testamentary trusts, adoption and divorce papers, certain court filings, and some notices cancelling utilities or insurance. Those still require wet ink.

Nearly every free PDF signing site works by receiving your file. You choose a document, your browser uploads the bytes, a server modifies the PDF, and you download the result. Your document exists on infrastructure you do not control for at least as long as that round trip, and usually longer — most services retain files for a window measured in hours or days so you can download them again.

This tool does not work that way. The PDF is read by your browser from your own disk, rendered to canvas with react-pdf, and modified in memory with pdf-lib. The signed file is produced on your machine and handed straight to your browser's download mechanism. No request carrying document content is ever made. You can confirm this yourself: open your browser's network inspector, sign a document, and watch that no upload appears.

The practical consequence is that there is no retention policy to read and trust, no stored copy to be breached, and no third party who could be compelled to produce your file — because no third party ever held it. For a permission slip that is a nicety. For a medical record, a salary offer, a document under legal discovery, or a scan of a passport, it is the entire point.

There is one trade-off worth naming. Because the work happens on your device, very large or image-heavy PDFs are bounded by your own available memory rather than by a server. The tool accepts files up to 25 MB, which covers the overwhelming majority of documents, but an unusually large scan is worth compressing before you sign it.

If your PDF will not load at all, it is almost certainly password-protected. Encrypted PDFs cannot be modified until the password is removed, so unlock it first and then come back to sign.

If your signature looks jagged in the finished file, the usual cause is drawing it very small and then scaling it up. Draw at a comfortable size and resize downward instead — shrinking a large signature preserves the detail, enlarging a small one cannot recover it. A trackpad also produces a noticeably rougher line than a touchscreen, so signing on a phone or tablet is often the quickest route to a clean signature.

If the document is a scan — an image of a page rather than real text — you can still sign it, because the signature is drawn on top rather than inserted into a text layer. You will not, however, be able to select or search the underlying text. Running OCR first turns the scan into a searchable document, which matters if the signed file needs to be findable later.

If your signature shows up in one PDF viewer but not another, that usually means it was stored as an annotation rather than merged into the page. This tool avoids that by flattening signatures directly into the page content with pdf-lib, so what you see on download is what every viewer renders — Adobe Acrobat, macOS Preview, Chrome's built-in viewer, and mobile readers alike.

And if pages appear sideways or upside down, correct the rotation before signing. Placing a signature on a page whose displayed orientation differs from its stored orientation can leave the mark in an unexpected spot once the rotation is fixed.