Everyday PDF tasks

PDF signature images and certificate signatures explained

Understand visible signature marks, certificate checks and the effect of changing a signed document.

RedactNinja guide. Updated 23 September 2026.

A signature drawn or placed on a PDF and a certificate-based digital signature are different things. They can look similar on the page, but the visible appearance does not tell you how the file was signed.

A visible signature mark

A typed name, drawn signature or imported signature image is page content. It may be appropriate for a workflow that accepts that kind of mark, but it does not itself provide cryptographic evidence that the document has remained unchanged.

Only apply your own signature or one you are authorised to use. Check the recipient's requirements before sending the file. RedactNinja does not decide whether a particular form of signature satisfies a legal or organisational requirement.

A certificate signature

A certificate signature connects a cryptographic signature to signed document bytes. Validation may involve more than checking that those bytes match: certificate trust, validity dates, revocation information and timestamps can also matter.

A mathematically intact signature is not automatically a trusted identity. A self-signed or unrecognised certificate can produce a signature whose integrity is checkable without establishing that the signer is the person you expect.

Before signing

1. Finish the content, page order and intended form entries before signing.
2. Check the recipient's accepted signature method and any certificate requirements.
3. Keep a copy of the unsigned source. Protect certificate files and their passwords; do not send them to support.
4. After signing, reopen the downloaded PDF and inspect it in a viewer appropriate to the recipient's validation requirements.

What happens if you edit afterwards?

Rewriting, merging, converting or compressing a signed document can affect its signature. Some PDF workflows allow particular incremental changes, but you should not assume that an arbitrary editor preserves those permissions or the original signature's status.

If you need a revised document, retain the signed original as evidence and create a separate revised copy. Check the final file rather than relying on a signature image that still appears on screen.

Limits of local checking

A purely local inspection may not have current revocation information or the trust configuration used by the recipient. Adobe explains how verification information can be unavailable when signing offline. An unknown or unavailable result is not the same as a valid result. Do not claim that signature inspection establishes identity, legal validity or long-term trust in every case.

Requesting signatures from other people, tracking their responses and managing shared signing records are separate services. A locally placed mark should not be presented as that kind of managed signing workflow.