I have worked at a couple of different startups and none of them had any formal design review process/protocol in place. Is it true generally for startups?

Which tools do you use mostly to write a design document (Other than Google Docs)?

Design review means:

- Someone writes a requirement doc - Engg then writes a design documemt - Peers then discuss and review this doc - Finally peers approve it and implementation starts - This doc then serves as reference throughout the implementation.