It has to be formatted to allow you to fill it out. If it is, then you just click in the fields and enter your data. I have, however, only seen one form like that in all of my computing days.
You must understand that a pdf is a glorified picture. Sometimes you can "write" on that picture or even search it for certain data. Having said that, it is possible for you to convert a PDF document to a word processing document. I don't know if the Adobe Pro does it, but I do know that you can do it with any myriad of distros of PDF viewers on linux. Get in touch with a computer junky that you know and have them convert it to Word for you, then you can edit it as you wish.