Are there anyways 'mouse hovering' can be used to display further information on 'specialy marked' fields in a form? A little bit like the 'screentips' feature in Word.
I'm assuming you are referring to Adobe FormsCentral and not Acrobat. If you select a field within the Design tab the properties panel on the right will show an "Include Help Text" check box. Checking that will create a "?" bubble to the right of a question that people can hover over to see additional information.