The upfitter manuals are text searchable PDFs. Do a search on what you are looking for. After you play with it a bit, you may learn some shortcuts to searching.
In the case of the brake controller, a search on "controller" is going to bring up all of the controllers on the truck, so, not so good. A search on "brakes" will bring up truck brakes as well as trailer brakes, so not so good. A search on "trailer" should narrow it down a bit better.
I also have learned that if you know a particular circuit or fuse, that can help. Unlike this website that requires searches to be for 4 characters or more, Adobe Acrobat allows a search on as little as 3 characters. So, since fuse F27 is used on the brake controller as I remember, a search on "F27" may put you on a useful page.
Note: all of my criteria in quotes, like "F27" do not require you to use the quotes, I was just using that to set off the search parameters.
Finally, I think the ultimate thread on installing brake controllers on these trucks was started by @Reverendbiker
, here is his thread.
DIY Brake Controller Hookup
2015 Canyon SLT, Copper Red, 2WD, CC, SB, V6, Tow, blk leather, factory spray liner, safety pkg, generic roll up bed cover, Tekonsha P3 Brake Controller.