MAC
To ZOOM IN (Increase Magnification): Press the SHIFT key.
To ZOOM OUT (Reduce Magnification): Press the CONTROL key.
To DRAG image (in ZOOM mode): Press the OPTION key, and drag with the mouse/tablet.
To FIT TO SCREEN: Press the COMMAND+3 keys.
PC
To ZOOM IN (Increase Magnification: Press the SHIFT key.
To ZOOM OUT (Reduce Magnification): Press the CONTROL key.
To DRAG image (in ZOOM mode): Press the CONTROL+ALT keys, drag with the mouse/tablet.
To FIT TO SCREEN: Press the CTRL+3 keys.