Be a bit cautious about the G-codes listed in the
github location Kirk (Mooselake) pointed to, or anywhere else for that matter. For example, the Printrboard does not have the native capability to turn the power supply on and off (M80 / M81) nor does it have the capability of turning the on-board LED on or off (M42). There are a number of other features not supported by the native Printrboard.
On the other hand, the list given there is incomplete regarding some specific Printrbot implementations for the Printrboard.
M211 X(value) Y(value) Z(value) for setting the boundaries of the printable volume in EEPROM. This command is not present in all Printrbot versions, and rarely if ever in mainstream Marlin; unfortunately the boundaries of the printable volume for most versions of Marlin is set in source code and you need to re-compile to change the boundaries. Printrbot's M211 is not compatible with the G-code at RepRap.org/wiki/g-code.
M907 X:(value) Y:(value) Z:(value) E:(value) sets the digipots. X, Y, Z, and E are all optional. Value is 0 to 100 (percent)
M909 Read the Digipots
M910 Save the Digipot settings.
Note: in a manner similar to Active Values for calibration, digipot settings can be changed with M907, but will be forgotten after a power-down. M910 saves the values in Digipot EEPROM (which is separate from all the other EEPROM storage).