How to Electronically Sign a PDF, and Whether It Is Legally Binding

Someone emails you a contract and asks you to "sign and send it back". You could print it, sign it with a pen, scan it and email the scan, or you could sign the PDF electronically in a minute. The obvious question is whether the electronic version counts. In most countries and for most everyday documents, it does. But there are real exceptions, and the evidence around a signature matters as much as the signature itself. This guide explains the law in plain terms, the difference between electronic and digital signatures, and how to sign a PDF in a way you can stand behind later.

This is general information, not legal advice. If a lot depends on a particular document, check the rules that apply to it.

Electronic Signatures and Digital Signatures

The two terms are often used as if they meant the same thing. They do not.

An electronic signature is any electronic mark or process that a person attaches to a document with the intention of signing it. A typed name, an image of a handwritten signature, a signature drawn with a finger, and an "I agree" checkbox can all be electronic signatures.

A certificate-based digital signature is a particular technical kind of electronic signature. It uses a digital certificate issued by a certification authority, often after an identity check, and seals the document cryptographically. PDF readers can verify it and will show a message such as "signed and all signatures are valid". If the document is changed afterwards, the reader shows that the signature is no longer valid.

Most everyday signing uses the first kind. The second is needed where a law, a regulator or the other party specifically asks for it.

What the Law Says, in Brief

United States. The federal ESIGN Act and the Uniform Electronic Transactions Act (UETA), adopted by almost every state, say that a signature may not be denied legal effect just because it is electronic.
European Union. The eIDAS Regulation recognizes three levels: simple, advanced and qualified electronic signatures. A simple electronic signature cannot be rejected as evidence just because it is electronic. Only a qualified electronic signature, made with a qualified certificate, automatically has the same legal effect as a handwritten one across the EU.
United Kingdom. Electronic signatures are accepted for most documents. The Law Commission confirmed in 2019 that an electronic signature can validly sign a document where the person intends to authenticate it, though deeds have additional rules about witnesses.
Elsewhere. Many countries have similar laws, often modelled on the same principles, but the details and exceptions differ.

What Makes an Electronic Signature Hold Up

Being legally valid in principle is not the same as being easy to prove. If a signature is ever disputed, the questions are usually these:

Intent. Did the person mean to sign, rather than, say, clicking past a screen?
Consent to sign electronically. In the United States in particular, the parties need to have agreed to do business electronically.
Attribution. Can the signature be linked to the person? A typed name proves little about who typed it, so the surrounding evidence matters: the email it came from, the conversation before it, and the way it was sent back.
Integrity. Is the document the same one that was signed, or has it been changed since?
Records. Can everyone involved keep and produce an accurate copy of what was signed?

Documents That Usually Need More

Some documents cannot be signed with a simple electronic signature, or need a witness, a notary or a qualified signature. Under ESIGN, for example, the exceptions include wills, codicils and testamentary trusts; adoption, divorce and other family law matters; court orders and official court documents; notices that utility services will be cut off; notices of foreclosure or eviction on a primary residence; cancellation of health or life insurance; product recall notices; and documents that must accompany hazardous materials.

Property transfers often go through a notary, and many countries have their own rules for documents filed with government bodies. The other party can also simply require a particular method: a bank or an authority may accept only its own signing system or a wet signature. When in doubt, ask the person who will receive the document what they accept.

Signing a PDF With Sign PDF

Our Sign PDF tool runs in your browser. Your PDF, your signature and the optional record page described below are not uploaded. Here is how it works:

Open the PDF. The pages keep their original size and their text stays selectable.
Type your name to build a typed signature, and pick a handwriting style and ink color.
Drag the signature onto the page. You can also add a date, in the format you choose, and an image such as a company stamp. A PNG with a transparent background stays transparent.
Tick the box that says "I intend to sign this document electronically and agree to do business electronically." The download stays disabled until you do.
Choose whether to attach a Signature Certificate page, then download the signed PDF.

The Signature Certificate is an extra final page that records the signing: a document reference, the file's name, size and page count, the time of signing, what was placed on which page, the consent wording and when you agreed to it, and two SHA-256 fingerprints. One fingerprint covers the source file as you opened it. The other covers the signed PDF as it was produced, before the certificate page was attached.

A fingerprint is a fixed-length summary of a file's bytes: change one byte, and the fingerprint changes completely. Anyone holding the original file can check it against the certificate. On Windows, the command certutil -hashfile contract.pdf SHA256 prints a file's fingerprint, and on a Mac or Linux shasum -a 256 contract.pdf does the same. A matching fingerprint shows the file is the one described. A different one shows it has been changed. Fingerprints reveal changes; they do not prevent them.

Sign PDF does not create a certificate-based digital signature, it does not verify who you are, and it does not record your IP address or email address. We also keep no copy of the signed document, so we cannot provide one later as evidence. Your own records are the evidence.

Habits That Make a Signature Easier to Rely On

Send the signed PDF from your own email address, in reply to the message that asked for it, and keep that thread. It links the signature to you.
Keep the unsigned original as well as the signed copy, so that the source fingerprint can be checked against it.
Do not edit the PDF after signing. If the terms change, sign a new version.
Sign only in your own name, or with the clear authority of the person or company you sign for.
Know what the tool is for. Sign PDF signs a document yourself. It does not send documents to other people for signature or collect their signatures, so each party signs their own copy and sends it back.

Conclusion

An electronic signature on a PDF is legally valid for most everyday documents in the United States, the European Union, the United Kingdom and many other places. What makes it dependable is the evidence around it: a clear intention to sign, agreement to sign electronically, a link to the person, and a record that shows the document has not changed. For wills, court documents, property and anything that requires a witness, a notary or a qualified signature, use the method the law requires.

Need to sign a document? Try Sign PDF.

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