We are a paperless office. Applicants should not use snail mail (teachers/counselors may be forced to if your school forbids online submission of their docs).
Common App schools have to ability to turn a resume upload function on or off. If you don’t see the ability to upload a resume, it means the school wants you to use the Common App activity section and not a resume.
As with most questions, there’s a post on the UVa admission blog about this!
http://uvaapplication.blogspot.com/2014/12/sending-resumes-to-uva.html