I got a ZenWatch 2 yesterday, and it comes with the following paper manuals (they are easy to overlook since they are thin skinny rectangles tucked tightly on the side of one of the skinny rectangular box compartments inside the larger box). They are: Asus ZenWatch 2 Quick Start Guide, Asus ZenWatch 2 Parts and Features Guide, and Asus ZenWatch Warranty Card.
The "fan" website has a lot of FAQ that cover things that can be found in the manual as well as a few other things: Forum-ZenWatch