Can font size be changed using Shortcut Key combinations ?

Yes, why not. The font size can be changed easily by using shortcut key combinations in Microsoft word. This shortcut is very useful as it saves a lot of time.  The shortcut key combinations are as follows: 

Ctrl + ]   (Increase font size)

Ctrl + [ (Decrease font size)

OR

Shift + Ctrl + > (Increase font size)

Shift + Ctrl + < (Decrease font size)

Stay Active for more interesting shortcuts!