[Update]: I have found a solution to remove the markup area instead of hiding it.
When you try to print your document in Microsoft Word 2013 (I’m now using Microsoft Word 2013 beta version), be warn that there maybe a huge blank space on the right hand side which is colored in light silver / gray color. This may happen when you have a long document. When I first encountered this problem, I was shock as there was no such blank space on the right in my document and the page layout was set correctly in Word. Later I found out that this blank area is call Markup Area where users can write their comments, highlights or changes at there. Although I didn’t write any comment there, yet the Markup Area show up every time I try to print the document.
I have no idea why this is turn on by itself, but if you want to get rip off that Markup Area, just go to Review at the top of the menu, look for Simple Markup, change it to Original. This should fix the problem and hide the markup area when you try to print your document.