Security
Why a picture of a signature is not a signature
A drawn, typed, scanned or pasted signature is a picture on the page. Pictures can be copied and moved, and nothing in the file records if the text around them changes. A digital signature is invisible proof inside the file that the document has not changed.
You uploaded a document to Verify PDF Signature. You can see the signature. The tool says "No digital signature found in this file".
What the tool does tell you
It does not just shrug. It looks at the page and tells you what is actually there, in sentences like:
- *"We found what may be a signature image on page 3. It is a picture, not a digital signature."*
- *"We found a hand-drawn mark on page 2. It is a drawing, not a digital signature."*
- *"We found a stamp on page 1. It is a picture, not a digital signature."*
- *"This file has a signature field that was prepared for a digital signature but never signed."*
That last one is worth noticing: somebody set the document up for signing, and nobody signed it.
Why a picture proves so little
A picture on a page is pixels. Which means it can be:
- copied from one PDF and pasted into another,
- moved to a different page,
- left exactly where it is while the text above it is quietly changed.
That third one is the dangerous one. Change "1,000" to "9,000" on an invoice and the signature image underneath looks perfect. Nothing in the file records that anything happened.
This is not a flaw in any app. It is simply what a picture is.
The everyday version
Two ways to send a letter.
- A picture of a signature: you sign the bottom of the page. Anyone who gets the page can photocopy your signature onto a different one, and the paper cannot tell.
- A digital signature: you seal the envelope with wax. If anyone opens it and changes a word, the seal is broken and everyone can see.
Both are real. Only one survives an argument.
So is a drawn signature worthless?
Absolutely not: and this is the part people get wrong in the other direction.
For a great many everyday documents, a drawn or typed signature is exactly what everyone expects and accepts: leave forms, delivery notes, club memberships, internal approvals, a great many ordinary contracts. It shows who agreed. In many countries it is legally an electronic signature.
What it cannot do is prove afterwards that nobody changed the document.
What actually protects a document
Two different things, and they can be combined:
A digital signature. Made with a certificate. Any change (one character) makes it show as invalid. Use Digital Signature.
An evidenced signing process. The document goes out through a system that records who opened it, when, from where, and gets it back with a certificate of completion and a seal. Use Request Signatures. See what a certificate of completion contains.
The first proves the file; the second proves the process. Serious agreements often want both.
Why files lose their digital signature
Sometimes a document genuinely was digitally signed and the tool still finds nothing. The usual causes:
- The file was printed to PDF or exported again. That rebuilds the file from scratch, and a digital signature cannot survive being rebuilt. The visible stamp often survives while the signature is gone.
- It was flattened or re-saved by an editor.
- It was edited after signing by software that removed the signature rather than preserving it.
If you expected a signature and there is none, ask the sender for the original file they signed, not a copy that has been through another program.
What to do next
- If you need proof that a document is unchanged, ask for it to be digitally signed.
- If you just need a signature on a page, Sign PDF does that in seconds.
- If you want a record of who agreed and when, send it through Request Signatures.
- For the full comparison, read what is a digital signature in a PDF.
Common questions
Why does the checker say there is no digital signature when I can see one?
Because what you can see is a picture: drawn, typed, scanned or pasted onto the page. A digital signature is invisible proof inside the file, and this document does not contain one.
Is a drawn or typed signature on a PDF legally valid?
Often yes, as an electronic signature, and it is accepted for a great many everyday documents. What it cannot do is prove the document was not changed afterwards.
Can a signature image be copied onto another document?
Yes. It is a picture, so it can be copied, moved or kept in place while the text around it is changed. Nothing in the file records that.
I scanned a signed paper. Is that a digital signature?
No. A scan is a photograph of the page, and the signature is part of that photograph.
My PDF was digitally signed but the checker finds nothing. What happened?
It was probably printed to PDF, exported, flattened or re-saved. Those steps rebuild the file and remove the digital signature while often keeping its visible stamp. Ask the sender for the original.
What should I use if I need real proof?
Sign with a certificate using the Digital Signature tool, or send the document through Request Signatures for a recorded, sealed signing process. Serious agreements often use both.