In Windchill 10 the formal User Guides are no longer published as documents. 
It was available in Windchill 9 http://www.ptc.com/WCMS/files/57569/en/PJLUsersGuide9.0.pdf
I guess this makes sense since the content is ever changing and was getting very large for User Guide.
The content is available in the online help. Unfortunately this means you need to have the application installed or search through the tech support site. You can also use the online, LMS training https://precisionlms.ptc.com/
