The signature for the Application.MailMergeAfterRecordMerge event looks like this:

        void Application_MailMergeAfterRecordMerge(Word.Document Doc)
        {
        }

While I would have expected the Document referenced in the Doc parameter to be the newly created merged document, it is actually a reference to the document from which the merge occurred. In other words, it’s not really all that useful.