In order to add Company's representative you need to take steps described below.
Go to Phonebook (click on wrench-icon on the menu-belt) and edit previously added Company (or add a new one).
At the bottom click Show company contacts and add details: name, surname, email address & phone number.
In section Planned Flights edit a trip and in the tab 'Trip Info' select a Client from the drop-down box (Leon will show companies and persons from Phonebook with the checkbox 'Client' marked).
'Client' can also be assigned in Edit Flight screen, tab 'Sales'.
Company's representative will appear on Flight Brief and Charter Contract document.