Setting automatic validation of digital signatures in Adobe Acrobat Reader DC

Download LRZ Root Certificate

Download the following file from the LRZ  : https://www.pki.dfn.de/fileadmin/PKI/zertifikate/T-TeleSec//GlobalRoot_Class//2.crt

Import and validate LRZ root certificate

Click in Acrobat Reader under Signatures on the right side under Identities and trusted certificates  by clicking on  More.

Select Trusted certificates on the left side and click on Import in the tab above.

Select the certificate T-TeleSec GlobalRoot Class 2 from the LRZ under Browse.

Select the location of the download certificate from the LRZ and click Open.

Under Contacts, select the certificate by clicking on it.

In the same window under Certificates, select the T-TeleSec GlobalRoot Class 2 certificate.

Then click on Trust

Check the box Use this certificate as trusted root in the window that appears.

Import the T-TeleSec GlobalRoot Class 2 certificate from the LRZ

Confirm the import with OK.

Then you can close all windows.