Can nuvigil be used to help with ADHD in adults?

Maybe. Nuvigil is a derivative of provigil. Provigil has been shown to be effective in treating adhd in several well done reports, eg, psychiatry res. 2009 aug 15;168 (3):234-7. E pub 2009 may 12. Similar studies are pending on nuvigil, so its use would be as a third line if other treatments fail.
Off-label. Years ago, mcneil pharmaceutical company did several trials in children that showed effectiveness of "provigil" about 65% of the time, about the same as strattera (atomoxetine). Two days after the last study, one child developed stevens-johnson syndrome. Although it could not be proven that it was a severe allergic reaction to the "provigil, " the fda pulled their approval. It costs ~ $600/mo. Without insurance.
Yes. While the fda has not evaluated the effectiveness of Nuvigil in add/adhd, Nuvigil can be trialed in adults. Typically it is utilized in those unable to take true stimulants eith due to side effects, concerns over abuse, or induction of mania. In my experience the results are not always as robust. Cost and insurance coverage can be an issue as well.