When trying to display the PDF invoice received from Isabel, it can happen that you see the warning ‘At least one signature has problems’.
This can happen when viewing documents through Zoomit, but also for already downloaded documents.
The solution is to add the certificate for the “Isabel Invoice Signer” to the trusted certificates:
Click on Signature panel
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In Signatures Select the Signed by Isabel Invoice Signer Signature
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Click on Validate Signature
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Click on Signature Properties
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In the Signature Properties, Select Show Signer's certificate...
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Go to the Trust Tab and in the left pane, Select the Isabel Invoice Signer certificate
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Click on Add To Trusted Certificates
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Click on OK
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And in the next window, Check Use this certificate as a trusted root and Click on OK
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Close the PDF document and open it again. The Signatures are now signed and valid
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