Page Up / Page Down - Changing scroll length on Yosemite

I have come to inquire about a terminal command to edit/change

the amount of scroll length Yosemite does when page up or page down is pressed.

For my knowledge, I think default value is one whole page.

I am trying to reduce the scroll length to improve on reading off web.

So, is there a command that can be put in terminal to change this?