Are two signatures needed on the updated visa submitted in the U.S. if acting on another parties'?

The last page of the updated (form V 2013) Chinese application has two places for signatures: one box for the applicant and another box for the person acting on their behalf. I have to submit applications for a party of five who are out of town (I have their info needed to complete the forms). I want to know do I need their signatures along with my own in order to fill out and submit their applications and pick up their visas or will just my signature suffice?