Complex sentence: New blue-line prints would then be made of the modified master, and the process continued, until upon completion of the project, the master with all changes incorporated, and authorizing signatures affixed, would be archived in a vault.
Split into simpler sentences: New blue-line prints would then be made of the modified master, and the process continued in this iterative manner until completion of the project. The master incorporating all changes and with authorizing signatures affixed, would be archived in a vault.