How to Sign a PDF Online (Step by Step)

There are two situations people mean by “signing a PDF online”: signing a document yourself, and sending a document to someone else to sign. Both take a couple of minutes in any modern e-signature tool. Here’s how each one works, and how to make sure the result actually holds up.

Option 1: Sign a PDF yourself

1. Choose an e-signature tool and upload your PDF. Most tools accept PDF, and many accept DOCX and images too.
2. Place a signature field where you need to sign. Some tools, including Signatura, can auto-detect where fields belong so you don’t have to place them by hand.
3. Add your signature — draw it with a mouse or finger, type it in a signature font, or upload an image of your signature.
4. Fill any other fields — date, initials, text, checkboxes.
5. Finish and download the completed PDF. A good tool seals the file so any later change is detectable.

Option 2: Send a PDF for someone else to sign

1. Upload the PDF you want signed.
2. Add signers by email. If more than one person needs to sign, choose whether they sign in order (sequential) or at the same time (parallel).
3. Place fields for each signer — assign each signature, initial, date, or text field to the person who should fill it.
4. Send. Each signer gets an email with a secure link and signs in their browser. They don’t need an account with the tool.
5. Track and receive the completed document. When everyone has signed, all parties get the finished PDF, ideally with a certificate of completion and an audit trail.

Make sure the signed PDF is legally binding

Signing a PDF is only useful if it holds up later. Three things make the difference:

• Intent and consent. The signer takes a deliberate action to sign and agrees to do so electronically. This is a requirement under the ESIGN Act and eIDAS.
• An audit trail. The tool records who signed, when, and from where (timestamps and IP), for every action.
• A tamper-evident seal. The completed document is sealed — for example with a SHA-256 hash — so any modification after signing can be detected. A hash proves the file hasn’t changed, which is not quite the same thing as a digital signature — that term means a key pair and a certificate, and the two get confused constantly. Signatura seals every completed document and lets anyone re-verify it; see how we secure documents.

A photographed or scanned signature has none of this, which is why a dedicated e-signature tool is far stronger evidence than emailing a picture of your signature.

Frequently asked questions

Can I sign a PDF online for free?

Many tools offer a free trial or a limited free tier for signing a small number of documents. Signatura includes a 14-day free trial with no credit card. For ongoing or team use, you’ll typically need a paid plan.

Does the other person need an account to sign?

No. With most e-signature tools, signers receive a link by email and sign in their browser without creating an account. Only the person sending documents needs an account.

What file types can I sign?

PDF is universal. Many tools, including Signatura, also accept DOCX and image files (PNG, JPG) and convert them to a signing-ready format, then deliver a sealed PDF at the end. Signing a Word file specifically? See How to sign a Word document electronically.

Is a signature I draw with a mouse legally valid?

Yes. A drawn, typed, or uploaded signature can all be valid electronic signatures, as long as there’s intent to sign and the signature is associated with the document. See Are electronic signatures legally binding?

How do I make an electronic signature in the first place?

You don’t need one in advance — the signing step creates it. Every mainstream tool offers the same three ways when you reach a signature field: type your name in a signature font, draw with a mouse, trackpad or finger, or upload a picture of your handwritten signature. If you want a reusable image, sign on white paper and photograph or scan it — or draw it once in a signing tool and save the result. And keep the picture in perspective: it is the least load-bearing part of an electronic signature. What makes it count is the intent and the record behind it — the certificate of completion, not the artwork.

Can I sign a PDF on a Mac without Adobe Acrobat?

Yes — macOS ships with it. Open the PDF in Preview: its Markup tools include a sign option that creates your signature from the trackpad, or from a signed piece of paper held up to the camera; place it, save, done. Two honest caveats. The result is a picture of a signature on a file — perfectly fine where the stakes are low, but it carries no audit trail or tamper-evidence, which is what separates a valid signature from a provable one. And if the document needs someone else’s signature, Preview can’t route it to them — that’s the send flow in how to send a document for someone else to sign.

Does the PDF need to be witnessed or notarised?

Usually not, and signing it electronically doesn’t change the answer. Neither the ESIGN Act nor UETA creates a witnessing or notarisation requirement — where one exists it comes from the document type or state law. So the question is whether this document would need a witness or notary on paper; if it wouldn’t, going electronic doesn’t add one. Where notarisation is required, the ESIGN Act provides that the requirement can be satisfied electronically when the notary’s own electronic signature is attached to the record. We cover witnessing, notarisation and remote online notarisation in Does an electronic signature need a witness or notary?

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Ready to try it? Start a free trial of Signatura or read about how we keep documents secure. Comparing tools? See how to choose a DocuSign alternative.