User Configuration > Administrative Templates > Microsoft Office 2016 > Security Settings > Digital Signatures
User
HKCU\software\policies\microsoft\office\16.0\common\signatures
This policy setting lets you specify whether or not Office 2016 checks the XAdES portions of a digital signature, if present, when validating a digital signature for a document. If you enable this policy setting, Office 2016 checks the XAdES portions of a digital signature when validating it. If you disable or do not configure this policy setting, Office 2016 only validates XML-DSig and XAdES-BES portions of a digital signature.