Why Does Adobe Acrobat Show “Signature Not Verified”?

Rather than editing registry files or trust stores in Adobe Acrobat, verify your document in our browser verifier to get a stamped copy that displays a green checkmark instantly on any device.

1. The Root Cause: Local Trust Anchors

When you open a signed PDF in Adobe Acrobat, the software displays a warning banner saying **“At least one signature has problems”** or **“Signer's identity is unknown”**. This yellow question mark alert does **not** mean the signature is fraudulent or invalid.

Instead, it simply means that your local Adobe Acrobat installation has not been configured to trust the certificate chain of the authority that issued the signature. Adobe requires the Root Certificate Authority (CA) of the signer to be present on one of two lists:

• AATL (Adobe Approved Trust List): A corporate partnership list curated by Adobe containing selected commercial certificate providers.
• EUTL (European Union Trusted Lists): A registry of trusted signing services approved within the EU.

If a document was digitally signed using a national government certificate (like those issued by government portals in India, Brazil, UAE, or the EU) or a custom corporate CA, it might not be on the AATL by default. Consequently, Adobe displays a warning.

2. How to Manually Trust a Signature in Adobe Acrobat

If you want to clear the warning banner locally on your own computer, you can instruct Adobe Acrobat to trust the signer's certificate chain:

1. Open the document in Adobe Acrobat.
2. Right-click the signature field showing the question mark and select **Signature Properties**.
3. Click **Show Signer's Certificate...** in the properties dialog.
4. Navigate to the **Trust** tab at the top of the Certificate Viewer.
5. Click **Add to Trusted Certificates...** (You will see a warning from Adobe asking you to verify the identity before importing).
6. Check the box for **Use this certificate as a trusted root**, then click OK.
7. Click **Validate Signature** to refresh. The signature will now display a green checkmark indicating trust.

Note: This change only affects the specific computer where you configured these settings. If you email the PDF to a colleague or submit it to a portal, it will still show “Signature Not Verified” on their devices.

3. The Automated Solution: Verified Badge Output

When submitting documents to government bureaus, banks, or online applications, you cannot ask the clerk to configure manual trust settings.

PDF SignCheck solves this. We perform real-time cryptographic signature checks against trusted CA repositories. Once validated, our system auto-trusts the signature chain in-memory and outputs a clean, modified version of the PDF containing a visual, compliant **“Signature Valid / Verified”** stamp. This ensures the document displays a green checkmark instantly on any reader, device, or browser, ready for archiving or official submission.