Add a signature to a PDF: what you need to know

“Signing a PDF” can describe very different operations. In everyday use it often means placing the visual appearance of a handwritten signature on a page. In other contexts, an electronic or digital signature refers to a process designed to identify a signer and protect document integrity.

Adding a visual handwritten signature

Add a signature to a PDF lets you place a visual representation of your signature on a chosen page, adjust its size and position, and generate a new PDF. This is appropriate when the requirement is explicitly to complete the document visually.

What this does not do

An image of a signature is not, by itself, a cryptographic or qualified electronic signature. It does not automatically create a digital certificate, prove the identity of the person who placed it, or provide a mechanism that detects every later modification.

Legal, contractual or administrative contexts may impose specific requirements. If the recipient asks for a certified or qualified electronic signature, a dedicated service or device may be necessary.

Visual, electronic and digital signatures are not interchangeable

A visual signature is simply what appears on the page. “Electronic signature” is a broader concept for expressing agreement electronically. Some digital-signature systems additionally use certificates and cryptography to verify integrity and an identity associated with the certificate.

These levels provide different guarantees. A visible autograph on a PDF does not by itself tell you what legal or technical evidence exists behind the file.

Integrity is a separate property

A cryptographic signature can make later file modifications detectable. A signature image placed on a page does not provide that property by itself; it becomes a visual element of the generated PDF.

That does not make visual signatures useless. They are practical when the recipient expects a visibly completed document. The important point is not to attribute guarantees they do not provide.

Prepare a clean signature image

Avoid shadows, grey paper backgrounds and large empty margins. Use a source that remains sharp at the displayed size. If you need a logo, stamp or illustration rather than a signature, use Add an image to a PDF instead.

Privacy matters

A signature is personal information, and the document around it may be sensitive as well. Keep unnecessary copies to a minimum and review the destination before sharing. The guide PDF and privacy: edit a document without sending it to a server explains the Local First approach in more detail.

Key point

Adding a signature image is a visual document-editing operation. It must not be confused with a certified, qualified or cryptographically verifiable electronic-signature process.