How to sign a PDF

There are at least six ways to put a signature on a PDF, and they are not interchangeable. They differ in what you can prove afterwards, which matters far more than how the signature looks.

Method 1: Sign inside a dedicated e-signature platform

The sender uploads the PDF, places signature and date fields, and sends a link. The signer authenticates, reviews the document, and signs. The platform records who signed, when, from what IP and device, and locks the document against further changes.

Evidence: strongest of the mainstream options.
Effort: low for the signer, low for the sender after template setup.
Cost: per-envelope or per-seat subscription.
Use when: the document matters and you may need to prove the signing process later.

Method 2: Sign with a PDF reader's built-in tool

Most desktop PDF readers include a "Fill & Sign" style tool. You draw, type, or place an image of your signature, then save the file.

Evidence: weak. Anyone can alter the file afterwards and the change is undetectable. There is no audit trail.
Cost: free.
Use when: the document is low-stakes and you will not need to prove anything — internal forms, casual acknowledgements.

Method 3: Draw a signature in an image and paste it in

Sign a piece of paper, photograph it, remove the background, paste the image.

Evidence: the weakest. It proves nothing at all about intent — the image could have been placed by anyone, at any time, without the signer's knowledge.
Cost: free.
Use when: essentially never, for anything that matters. It is common, and it is a habit worth breaking.

Method 4: Print, sign, scan

The traditional route. Print the PDF, sign in ink, scan it back.

Evidence: moderate. A genuine ink signature on paper, but the PDF is a copy — the paper is the original, and the original is what a court wants.
Cost: paper, ink, time.
Use when: a counterparty or agency specifically requires wet ink.

Method 5: Certified digital signature with a certificate

You sign with a private key held in a certificate issued by a certificate authority. The signature is cryptographically bound to the document, and any later change makes verification fail.

Evidence: strongest overall — third-party verifiable without trusting the sender's platform.
Cost: certificate issuance and management.
Use when: non-alteration must be provable independently, or a regulator requires it. See electronic vs. digital signatures.

Method 6: Typed name with a recorded consent step

The signer types their name into a field and clicks an explicit "I agree to sign this document" control, with the event logged.

Evidence: better than most people assume. Intent is clear, the event is timestamped and attributable, and it is legally sufficient in most jurisdictions. This is, functionally, what many platforms capture under the hood.
Cost: whatever your platform charges, or nothing if you build it.
Use when: the platform supports it and the stakes are moderate.

Ranked summary

Method	Evidence strength	Effort
Certified digital signature	Highest	Setup required
Dedicated e-signature platform	High	Low
Typed name + logged consent	Good	Low
Print, sign, scan	Moderate	High
Reader fill-and-sign tool	Weak	Free
Pasted signature image	Very weak	Free

The rule worth remembering

Choose by what you would need to prove if the signature were disputed, not by how convenient the method is. For a document you will never think about again, a reader tool is fine. For a contract, a lease, an offer letter, or anything with money attached, use a platform that keeps an audit trail — and export that trail when the deal closes.