Is it possible to add help text to a form that would prompt (balloon, dialog flag, etc.) the user whenever the cursor entered the variouse fields?
This is something that is supported. To add help text select the field that you want to add the text to and in the Field Properties widget that appears to the right check the Include Help Text checkbox. You then add your text in the text input field that appears. For HTML forms this will add a question mark icon next to the field. When users click on it the text is displayed. For a PDF form the text will appear when the user hovers the cursor over the field.