That's not quite true Elgin. The full version of adobe acrobat supports the creation of form fields which can be filled out in acrobat reader (and also allows you to edit most existing documents, including the FIRST rulebook, for adding in rule updates). The forms can even do simple math, feature drop down boxes, and have most of the features you'd find in an HTML form. You can see an example of such a PDF document
here.
That said, I don't believe there is any free software that can create forms (although there is pay software out there that can do it and costs less than Acrobat).