Some PDF files are set up to be filled in when they are opened using a newer version of Adobe reader. Go to www.adobe.com and download the most recent version (I think it's 5.05). It's free.
Open the document using Reader. You click on the appropriate block and type in the info. Watch for your cursor to change from a hand to either a pointing finger or a type-in cursor when you hover over the check box or block .
Here's a link to an 8710 set up as a fill-in PDF which you can use to see if your program is set up properly. It works fine as an Adobe fill-in PDF on my computer.