My friend has same program and has Helvetica-I am not able to edit the PDF because she has Helvetica and my version (Academic) does not have it.
Acrobat doesn't come with Helvetica. The other person probably happened to own it anyway.
Helvetica is a standard MAC font. The equivalent on a PC is Arial. I am not sure if you can change the font (compatibility issue), but if you try that you might be able to edit.