Agree with most of the comments in this thread. If I'm very lucky then I'll get a generic manufacturer's manual that isn't of much use and some component manufacturer leaflets, which can be useful.
One of the first things I do with a new bike is take photos of all of the torque setting markings on the various bolts around the bike, and the tyre pressures marked on the tyre sidewalls. That generally gives me something to check and adjust as necessary before a first ride.
Most useful info can be found on forums and manufacturers websites.