For using xsetwacom to do it, look here: http://linuxwacom.sourceforge.net/wiki/index.php/Dual_and_Multi-Monitor_Set_Up#Coordinate_Transformation_Matrix
You basically have to do it by hand, calculating the proportions of your monitor and translating them to tablet size. The instruction in the link explain how to map the whole tablet to the screen, with distortion. It should be easy (if you get the math behind it) to adapt it to not distort.
BUT there are GUI apps too: http://linuxwacom.sourceforge.net/wiki/index.php/External_applications#Utilities
If you're on KDE you maybe want to take a look at the "Wacom tablet" settings module. It's not yet where the windows driver is, but it lets you do what you want, set different profiles and more. I must say that it's not working well for me on Debian Jessy, but the version on the repos is an pretty old. (You don't say what distro are you using, usually relevant in a linux question)
There's also a GNOME applet, never tried it, but seems good (even better?).