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.

- Open the PDF document in Adobe Reader showing the “At least one signature has problems” error.
- Click on the Signature Panel button, which will be on the right of the error.
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Click on the Validate all link. It will prompt the message to validate all signatures depending on the settings.
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Click OK to validate all the signatures. Once all signatures are validated it will show a success message depending on the settings.
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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.
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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.
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Click on the Show Certificate button, and a Certificate Viewer window will open from where you can see the details of the certificate.
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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.
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Click Add to Trusted Identities and when Adobe Reader asks if you are sure you want to add it click OK.
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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.
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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.
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Click on the Close button to close the Signature Properties window.