A few of the multi-touch features on Mac OSX affect the printing process and can cause a failed print.
Expośe (4 fingers up) affects the printing process.
The 3-finger swipe for changing desktops and going to dashboard affects the printing process.
Mission Control (5 fingers) is safe and does not affect the printing process.
2-finger gestures, such as scroll or double tap, are safe.
3-finger drag is safe.