We are using Active Directory Certificate Services (ADCS) and have issued certificates to users in our Domain. Using Acrobat X, I am able to create and sign a document using the certificate issued by ADCS, however whenever someone else in the organization opens the PDF, they get a "At least one signature has problems". Upon checking the properties of the signature, they see the "Signature validity is UNKNOWN" message. Now all the machines have the RootCA and the IssuingCA certificates on their machines and I can see it in the Windows Certificate store as well. Due to this, the chain of trust is also valid when you open the certificate as well. Can someone tell me what I'm missing here? What else do I need to do so at least users in my organization can successfully sign and validate each other's signatures? Any help/advice/comments are appreciated.