You really should provide more information if you want a useful response. Is the viewer going to be in a modal/modeless dialog or a separate program and have you considered these alternatives? Are the buttons you want to add going to be in a tool bar, plain buttons or owner drawn?

Keep it simple dex

Read Registry Redirector (Windows) and other related pages. The basic answer is yes and no. :) InProcServer32 is not reflected between 64 and 32 bit DLL registration so they can co-exist.

Keep it simple dex