How am I to provide a link when it is on your hard drive? Hmmmm? I know.....your computer does not exist. Learn to open your eyes and actually do computer stuff yes? Like um, look. Snoty git.
I tell you, even finding the main directory in a Steam installation is an adventure in its own right. I currently have three such, plus a few non-Steam GC installs. And why would I go looking when SD gives NO indication that there is anything to find there (as per Franton above).
Anyway, found 'Manual 2018'. It has three sections: Intrigue, Crusade, and Base Game 2.33 (which is what I was playing earlier). I have neither Intrigue nor Crusade installed. So which section pertains to 3.7? At least Intrigue has Cities...
For future reference, the likely link is:
file:///X:/Program%20Files%20(x86)/Steam/steamapps/common/Galactic%20Civilizations%20III/GalCiv3_Manual2018.pdf