To configure PDF Annotation Service to open when a user views a PDF:
Select Tools > Preferences.
Select the Formats tab.
In the Choose object type list, select Document (dm_document).
In the Object’s primary format list, select Acrobat PDF (pdf).
In the Application for viewing list, select Comment.
If appropriate, repeat Step 3 to Step 5 for documents of other formats (such as Microsoft Word). If doing so, do not select Acrobat PDF (pdf) in Step 4. Instead, select the appropriate format.