A Signature Picture Is Not a Digital Signature: What to Tell Users Before They Send a PDF

When a product says “digitally signed,” a user may reasonably expect more than a picture of a handwritten name. A visible signature mark and a certificate-based digital signature answer different questions, and a workflow should make that distinction before the file reaches its recipient.

This article was written by GPT-6.1 Terra for the LensUp publishing account, which is affiliated with LensUp, using public documentation. An independent AI editor polished the text on 14 November 2026. No PDF was signed or validated. The checks below are suggested support steps, not measured findings.

Name the action the interface actually performs

A tool may let someone draw a signature, type one or place a picture on a PDF. The resulting mark can communicate intent visually, but placing that mark alone does not add a certificate. For example, a Sign PDF workflow can add, move and resize a visible mark, then download an edited copy. Describing that action as “Add a signature mark” gives support staff and users a more precise account than promising certificate-based signing. That wording is a clearer name for the visible action, not a verified label for a particular button.

A certificate-based digital signature uses a digital ID and provides information that compatible PDF software can inspect. Adobe describes the certificate-based approach in its certificate signatures documentation. Whether a particular signature is appropriate or legally sufficient for a transaction is a separate question for the recipient and the relevant process.

The distinction is not a visual classification of an entire file. A PDF can contain both a signature picture and a separate digital signature. Conversely, a digital signature can be invisible. Seeing a handwritten mark does not prove that a certificate signature exists, and seeing no mark does not prove that one is absent.

Give support a useful handoff

Before a user sends the document, ask the recipient what type of signature is required. If the recipient wants a visible mark, explain how the chosen workflow adds that mark and produces an edited copy. If the recipient asks for certificate-based signing, direct the user to a workflow that actually performs it and to the recipient’s instructions for the required signer and certificate.

Keep the signed original. Do not rewrite, flatten or convert it and then describe the resulting file as though the original cryptographic validity necessarily persists. If a different version is needed, clarify with the recipient which file should be submitted.

Inspect the signature without changing trust settings

In Acrobat, open the Signatures panel, then use Options → Validate Signatures and examine Signature Validation Status. From the signature properties, Show Signer's Certificate provides certificate information. Interface details can vary by version; Adobe’s validation instructions provide the current product guidance.

Report what the software shows and pass unexplained warnings to the document owner or recipient. Do not instruct users to trust an unknown certificate, disable checks or dismiss a warning merely to obtain a reassuring status.