How to find Printrboard pin numbers in Marlin
As FarO suggested, from github:Printrbot/printrboard/revF2 (via RepRapWiki - Printrboard - Revision History), the EagleCAD board layout and schematics are contained in the printrboard-revF2.zip:


Printrboard.sch
Printrboard.brd


This is the EagleCAD schematic: 



EagleCAD board layout



Not quite the annotated diagram that you were after, unfortunately, but it might help.



There are a couple of configuration files on KevinOConnor/klipper, but unfortunately only for revisions B to D (at90usb1286) and G (SAM3x8c)... E and F are not available.