If the error "At least one signature has problems" appears in Adobe Reader it means that the security certificate Visma Addo is using is not added as a trusted identity in your Adobe.

1. Open the PDF document in Adobe Reader showing the “At least one signature has problems” error.
2. Click on the Signature Panel button, which will be on the right of the error.

3. Click on the Validate all link. It will prompt the message to validate all signatures depending on the settings.
   
   

4. Click OK to validate all the signatures. Once all signatures are validated it will show a success message depending on the settings.

5. If the signatures are successfully validated Adobe Reader will show the message Signed and all signatures are valid. If that is the case, you can skip the next steps.
   
   

6. If At least one signature has problems error is still visible, select the signature which has the problem and right-click on it. It will display a pull-down menu. Here, select Show Signature Properties in the menu, and the Signature Properties window is shown.

7. Click on the Show Certificate button, and a Certificate Viewer window will open from where you can see the details of the certificate.

8. From the Certificate Viewer window, click on the Trust tab, and you can now see the Trust settings. Here, you will see the This Certificate is not a trusted message.

9. Click Add to Trusted Identities and when Adobe Reader asks if you are sure you want to add it click OK.

10. Now it will display the Import Contact Setting window. Select Use this certificate as a trusted root checkbox and click on the OK button to import contact settings into your system.

11. Now the signature is validated and it will display Signature is VALID, signed by message in Signature Properties window which is opened in Step 6.

12. Click on the Close button to close the Signature Properties window.