Your best bet, if you want to try again with the app, is to download it to the iPad.
Then, without plugging in the iPad, open iTunes, find the offending app and delete it from iTunes (all the way delete ... IOW, say yes when iTunes asks you if you are sure and do you want to send it to the Recycle bin).
Then, plug the iPad into iTunes and left click on the iPad line [in the left column] - elect to "Transfer Purchases." The iPad will then transfer the freshly downloaded app over to iTunes.
This won't cost you anything to re-download...
Hope that answer your question. Let us know if you need more.
Marilyn