What am I doing wrong?…. PDF editor

I have downloaded a number of PDF editors today and I cannot seem to get any of them to work. It has to be something I am doing.. The current one I am working with is “cad-kas pdf editor 2.2”.
I do not have the full version of Adobe Acrobat ; only the reader 5.1.0. I cannot get any of these to edit the text. Some tell me to highlight the text… I cannot highlight any text…. Help Please……Windows 98SE….