Mouse-wheel operations
If you have a mouse with a wheel; you can:
 scroll the wheel to scroll 
 up and down
 scroll the wheel to scroll 
 up and down
 hold down Shift to scroll 
 left (scroll the wheel up) or right (wheel down)
 hold down Shift to scroll 
 left (scroll the wheel up) or right (wheel down)
 hold the wheel down to slide 
 the document around in the window
 hold the wheel down to slide 
 the document around in the window
 click the wheel to center 
 the view around the mouse pointer
 click the wheel to center 
 the view around the mouse pointer
 Shift-click to zoom out
 Shift-click to zoom out
 CTRL-click to zoom in
 CTRL-click to zoom in
 Hold down CTRL for variable 
 zoom in (scroll the wheel up) or zoom out (wheel down).
 Hold down CTRL for variable 
 zoom in (scroll the wheel up) or zoom out (wheel down).
Feather tool
You can control the feather slider with your mouse and keyboard. When the feather text box or slider are selected:
Mousewheel up/down—increases or decrease feathering
Mousewheel up/down while holding the CTRL key—increases or decrease in larger increments
Arrow up/down keys—increases or decrease feathering
Page up/page down keys—increases or decrease in larger increments
Hom/end keys—select minimum or maximum feather values