Preview is my default .pdf reader. But since I opened a .pdf file in Acrobat just now, whenever I open any .pdf file from Firefox, it downloads it and opens it with Acrobat. This is weird because when I double click on any .pdf files on my HD, it still opens it with Preview. Any idea how I can make Preview the default .pdf reader for Firefox?
Edit: When I go to Firefox>Preferences>Downloads>File Type, and try to change the applicatin for .pdf files, it wouldn't let me choose Preview for some reason...

And Firefox thinks Acrobat is my default .pdf reader, when in fact it's Preview. How can I change that?