How to Verify a PDF Digital Signature
Verifying a signature answers several separate questions. A visible tick drawn on the page is not one of them.
What verification checks
- Integrity: the document has not changed since it was signed.
- Identity and trust: the signing certificate chains to a certificate the viewer trusts.
- Time: when the document was signed — reliable only with a trusted timestamp.
- Revocation: whether the certificate was revoked, using revocation data from the network or embedded in the PDF.
In Dragdox
Open a signed PDF in Dragdox and it verifies each signature and marks the signature field: a green tick for Signature valid, a red cross for Signature invalid, and a question mark for Identity unverified. Open the signature to see its details (Overview, Certificate and Advanced).
Which certificates Dragdox trusts is managed in Settings → Trust Manager. Only add a certificate you have obtained from its issuer and trust. Never add a certificate just to turn a warning green.
In other viewers
Dragdox writes a standard PAdES (ETSI.CAdES.detached) signature, so Adobe Acrobat Reader and other PDF tools can verify it. On Linux, pdfsig document.pdf from poppler-utils prints the validation result for each signature. Each viewer decides trust from its own trust lists and settings, so the same file can show as trusted in one viewer and unknown in another.
The Green Tick option
The Green Tick option when signing is part of the signature’s visible appearance. It is drawn when you sign and is not proof of validity; the viewer’s own verification result is what counts.