Hi Susan,
Acrobat Reader 7 will enable all
http:// style links in any PDF - it's a feature of Reader 7. So
http://www.apple.com will be clickable whether or not it was in the document that the PDF was created from.
What this approach won't do is convert links that have been hidden behind words, such as putting the "Apple UK" as a link to the relevant website in your document. Unfortunately, like yourself, this is what most of us want to do!
Tiger makes no difference to this.
Hopefully Apple will listen, but I feel this will require a bit more work than they might like to do!
matt