As far as I'm aware the term ADD and ADHD represent the same condition, but the term ADD is outdated and no longer used in the DSM. Sometimes I wonder if it truly qualifies as a medical condition or if it's merely an aspect of personality. Diagnoses are at times questionable and while many people benefit from treatment, I think it as used by many as a performance enhancing drug of sorts. That being said, I can definitely see how NP types could be prone to symptoms ADHD.
In regards to myself, I was generally a good student throughout school. However, I found myself easily distracted and sometimes struggling to pay attention to topics that either didn't interest me or that I didn't feel were worth my time. I tended to procrastinate until the last minute with assignments and studying, if I studied at all. I remember standardized tests being the absolute worst... there was one specific test where my mind wandered somewhere far away... I didn't realize until they called the ten minute warning! I wonder, looking back, how much my scores would have improved had I been on Adderall or Ritalin. Later in life, I actually met with a psychiatrist where I filled out questionnaires for ADHD. I tested "extremely high" in all categories, but never received a follow up appointment for diagnosis and further testing because the facility never answered my calls. I suppose the problem wasn't enough to necessitate pushing it further. I think medication certainly would have improved certain areas of my academic career, but looking back I'm happy I never obtained a prescription for regular use. It forced me to deal with some of my worst habits... my apathy and lack of motivation.