Master documents are the base or main documents which all piping or other discipline personnels refers to them for their works. In some companies, there is independent Document Control software to control all reviews and comments, but in some other companies there is not such software.
Actually in this tool, all power users have access to these master documents for any comments or review. Also we are sure that all designers, stress analysis persons, support-mans and checkers have a same documents for their work.