Why can't I view and download PDF's?

Folks;

I keep having problems since I upgraded to Snow Lepard. Since the upgrade I have not been able to view or down load PDF's like statments from various organizations. It doesn't seem to make any difference which browser I use, Safari or FireFox. Before SL I was able to download these same files and view them in Preview. Any suggestions? Do I need Acrobat Reader?

Thanks

Cap2799