The header and footer areas are the parts of the printed page above and below the top and bottom margins. They can be filled with content, such as a page number or the title of the document—or they can be blank. Removing a header or footer will make the area blank; it won't change the margins. Here's how to remove all headers or footers:
On the Insert tab, click Header or Footer, and then click Remove Header or Remove Footer.
If your document has more than one section, repeat this process for each section.