I’m unaware of any updated document. The forums here are somewhat active so if you have questions people will try and help. I love playing with my smart phone next to me. In fact it is how I use these forums 97% of the time.

The manual is pretty good, though no single document can capture the detail in GC3.

The trick until recently, was finding the manual.  Many links point to the long-obsolete 1.03 version, which I suspect is the one you're looking at.  The current version is _2018.  With the 3.8 update, the manual icon on the game main menu screen (lower right) will bring it up in your default browser. 

Or you can find it in your local installation directory, which might turn into a snipe hunt since Steam buries its installation.  So a search for GalCiv3_Manual2018.pdf might be your best bet.

Now that you've found the manual, what section should you refer to?  Depends on what you have installed and running.

Ok the manual 3.8 is your best bet. I would state that the forums, and discord is a decent place to get help. Let's play videos will help. Also there is a little more outdated newbie, and other guides on steam.