How to remove additional background that doesn't contain any data ?

When scrolling in any direction I found that unused area

For example :
When scrolling up , I found unused 6 inches

How can I stop scrolling from going to unused area and make the scroll stops at the edge of page contents ??

It can be useful to go beyond the boundaries of the page whether to get colour to the edge, to have just a portion of the picture on the page, or usefully as a storage area for objects as you arrange or re-arrange them. Embrace the space.