Manuscript Preparation, Copyediting, and Proofreading

Q. I am the first and only technical writer at this company. Since they do not have any style guides, I know legally there are no issues in using the Chicago Manual of Style. But is it legally OK to use the Microsoft Manual of Style?

A. I suppose that depends what you use it for. (How heavy is it?)

[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]