Is there a way to get Adobe Acrobat Professional on Mac OS X to stop asking to be the default PDF viewer?

Is there a way to get Adobe Acrobat Professional on Mac OS X to stop asking to be the default PDF viewer?

Every time I open Acrobat on OS X 10.5, Acrobat asks to be the default PDF viewer, with no option to "remember this choice" or "not ask again" etc., and I can't find anything in the preferences either to disable asking, but it's quite rude as I have made it perfectly clear that I prefer Preview to open my PDFs!