If the form was made sensibly there'd be text input boxes for you to type directly into.
If not, tough luck.

Print and biro are your only 'easy' options.
You could open it in the proper Adobe Acrobat editor or Photoshop or Illustrator if you have any of these - and then add text boxes where you like to type into.
You could even print it to a post script file, open this in an appropriate editor and then edit this. It all gets a little bit silly at this point...

Edit: How big is the form?
If its not too much work I could add the text boxes for you as I have all the adobe stuff here.