How to sign a PDF electronically

Last updated October 22, 2026

Add a visible signature to a PDF, understand the difference between an electronic signature and a digital certificate, and know when the difference matters legally.

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Signing a PDF is a five-minute task. Understanding what you have produced is what stops it going wrong later, because “electronic signature” covers a wide range of very different mechanisms — from a picture of handwriting to a cryptographic proof of identity.

This covers the practical version most people actually need, and is explicit about its limits.

What you are producing

A visible electronic signature is, mechanically, an image placed on the page. That is not a diminishment — it is precisely what makes it useful. It is the digital equivalent of signing a printout: it records intent, it is visible to every recipient, and it travels inside the same file as the document.

It is not:

proof that the person who signed is who they claim to be;
a mechanism that detects later edits;
a cryptographic credential tied to an identity.

A certificate-based digital signature is all three of those things, and it requires a certificate and software that most people do not have. The two are often confused. They should not be.

The steps

Open the PDF in a signing tool.
Choose how to create the signature. Drawing with a mouse, trackpad or finger reads most naturally. Typing in a script face is neater but obviously not handwriting.
Place and size it. Signatures belong over the signature line, not below it. Keep it large enough to be legible at 100% zoom and no larger.
Add a date if the document expects one. Many forms have a separate date field; an undated signature invites a follow-up.
Save and check the result by reopening the downloaded file, not just the preview.

Two habits that prevent avoidable problems: sign in a colour that is clearly distinct from the printed form, and never leave a signature field blank on a form that has one.

What a visible signature does not protect against

Copying. The signature is an image. A recipient can extract it. If your signature image is used elsewhere, you have the same problem as a photocopied signature.

Alteration. Someone can edit the document afterwards and the signature remains visible. The image does not notice.

Repudiation. Without a certificate, there is no technical evidence tying the signature to you beyond the fact that it appeared in a file you sent.

For employment contracts, NDAs and ordinary purchase orders, that is usually acceptable — the legal weight comes from the commercial context, the email trail and the parties’ conduct. For documents where forgery or later modification is a real risk, only a certificate-based signature is appropriate.

The legal position, briefly

Rules differ by jurisdiction and by document type, so treat this as orientation rather than advice.

Framework	Region	What it does
ESIGN Act	United States	Gives electronic signatures the same legal effect as written ones for most transactions
UETA	Most US states	State-level counterpart to ESIGN
eIDAS	European Union	Defines tiers — simple, advanced, qualified — with different evidentiary weight

Two categories typically fall outside: certain family-law documents (wills, divorce), and some documents requiring notarisation or witnesses. If a contract specifies a signing method, follow it — a tool cannot override the agreement.

Signing on a phone

Mobile signing works, with two practical differences worth knowing before you try it.

A finger produces a thicker, less controlled line than a stylus or a mouse. For many forms that is fine; for a signature that needs to look consistent across documents, drawing once with a stylus and reusing it is more reliable than drawing again each time.

Placement is harder on a small screen. Pinch to zoom before positioning, otherwise a signature that looks centred at 40% will sit over the printed text at 100%.

When you need more than a visible signature

Choose a certificate-based digital signature when:

the recipient must be able to verify that the file has not changed since signing;
the signer’s identity needs independent proof, not just assertion;
a regulator, court or counterparty requires it;
a workflow depends on machine-verifiable signature validation.

That route needs a certificate from a trust service provider and software that supports PAdES or an equivalent standard. It is a heavier process, and for the documents most people sign, unnecessary.

Signing without handing over the document

A signature is personal data in a fairly literal sense, and documents that need signing are often the sensitive kind: leases, offers, medical consent forms.

The sign tool here draws the signature into the page inside your browser and saves the file locally. The document and the signature image never leave your device. You can verify it in the Network tab while signing.

One caveat worth stating plainly: because the signature is embedded as an image, keep the signed file somewhere you control. Emailing it onward is the point at which it stops being private.

Where to go next

If the signed document then needs to be prepared for filing, deleting pages or merging it with supporting documents are the usual next steps. For the broader question of what happens to files handed to online services, see is it safe to upload a PDF.

Frequently asked questions

How do I add a signature to a PDF?

Open the PDF in a signing tool, draw or type your signature, place it on the page where it belongs, then save. The result is a normal PDF with an image of your signature on the page.

Is an electronic signature legally binding?

In many jurisdictions, including the US under the ESIGN Act and most of the EU under eIDAS, a simple electronic signature can be legally binding for ordinary commercial agreements. Whether it is acceptable for a specific contract depends on the parties and the subject matter, and some documents still require a witnessed or notarised signature.

What is the difference between an electronic signature and a digital signature?

An electronic signature is a visible mark indicating intent to sign — an image of handwriting, a typed name, a click. A digital signature is a cryptographic operation that binds a certificate to the document so any later change is detectable. A PDF can have one without the other.

Can someone copy my signature image from a PDF?

Yes. A visible signature added this way is an image embedded in the document, so anyone who receives the file can extract it. Treat it like a scanned signature on paper rather than like a cryptographic credential.

Do I need a certificate to sign a PDF?

Not to add a visible signature. If you need tamper evidence or a verifiable signer identity, you need a certificate-based digital signature, which requires a certificate issued to you and specialised software.