Each overseer who has access to these outlines and other materials are given unique passwords which is different from his convention domain password. These passwords are shared through a letter sent to the Convention Committe Co-ordinator. Usually, the Audio-Video Overseer will share his password with a volunteer/key-man with whom he is working so as to print the talk outlines and use it during the video and demonstrations rehearsals before the convention
The branch can easily come to know which overseer has been assigned with this password which can land him in unnecessary trouble and pain.
So much secrecy. It's almost as if they Watchtower Society is a cult that likes to keep most of their members in the dark. <insert sarcasm here>