As Bob said Interactive pdfs have a very limited constituency as far as pdf readers go. The default pdf readers for Mac or PC can't read their interactivity and only Acrobat 9 or above are designed to work. If you don't want to follow Bob's advice and use a Google Form you can always include a warning line "If your pdf reader can't read this form's interactivity then please download the free Acrobat Reader program from Adobe.com".
If the only intent of your pdf is to have live links you can use InDesign's Hyperlinks and save as a Print pdf. At the very least these can be read by even earlier versions of Acrobat.