I hesitate to post this question, because it seems so stupid, but I'm really stumped.
I downloaded the latest ReaderRights credential 0004517_Exp20080430.pfx to the correct /sapmnt/N4S/global/AdobeDocumentServices/TrustManagerService/trust/credentials directory and attempted to apply it to the Visual Administrator service "Document Services Configuration".
"The password entered does not match the credential chosen. Please enter the password for the chosen credential".
Stopped/started J2EE server, made sure it was typed correctly, always the same. I can only imagine that the credential is not designed to be applied a second time, which is a bit a problem for a preview system.
Any ideas appreciated.