LORs
Only attach them to the app if the app's instructions say you may. Otherwise, if you do, two bad things could happen: (1) they could get lost or misplaced, or (2) it will be apparent that you cannot follow directions.
The only exception to that piece of advice might be if it is an LOR (s) from someone within the company. In that case, I might consider attaching them to the front of the application form, especially if the letter(s) are from company bigshot.
Bring copies of them to the interview and hand them to the interviewer.
Good luck with your interview.