thank you jeproks.
1. ngourlay suggests me to "buy the commercial version of Adobe Acrobat, rather than the free version." (why he suggest me to do so since i am only CONDUCTING A SURVEY??)
2. now you say that "pdf file format cannot be edited if the file is opened by a commercial adobe softwares like pro adobe V.7"
ok, anyway... I actually got the answer for my question..
as my hubby said: make it as simple as possible, keeping in mind that the maximum what the Operator will know is how to press the keys on the keyboard (IF!)
Thanks to everybody!


*********************
“You become responsible forever for what you have tamed”. Antoine de Saint-Exupéry