Question

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!

Answer 1

Try clicking yes to see if Acrobat remembers the settings, then ctrl-click on a pdf file, choose "Get Info".
From there, select your preferred software under "Open with:", then click the "Change All…" button.

If that doesn't work, maybe Acrobat preferences are corrupt and you should try deleting them.