The Manual is normally installed in a subfolder of your c:\Games\Rise of Prussia, called "Docs". Only English, French or German is available, sorry.
The game itself can be played in Spanish, and installed in this language....and that may be the reason (?) while you don't see the manual, as no Spanish manual exists...possibly an error of the installer (will need to check)
In the meanwhile, send me an email at email@example.com
and i'll send you a copy by mail