You can assign your own keyboard shortcuts to VSdocman commands. You can do it the same way as for other Visual Studio commands:
1.Go to Visual Studio Tools - Options...
2.Select Environment | Keyboard page.
3.Assign shortcuts to the following commands (enter "vsd" to Show commands containing field to filter out other commands):
•VSdocman.CommentEditor
•VSdocman.AddComment
•VSdocman.OpenVsdocman