[stomachmonkey]

PDF's can be used in the way you want, if the creator took the time to build it as a proper interactive form.

PDF's can be built from just about anything including a scanned paper document which would not be editable under any circumstances.

Even if you had Acrobat Pro you still might not be able to edit.

Part of the concept of a PDF is a readily distributable platform independent read only file.

Basically they don't want you to be able to edit it.