Microsoft Word lets you set your page margin for a document using the "Margins" button in the program's tool bar. This changes the entire document's margins, including the header, which can wreak havoc on your formating if you do not want the header and body of the document to have matching margins. You can, however, work around this problem. Manually set the margins of your header using the left and right indentation tools as well as the header's own top and bottom margin options.
Double-click the Word document's header.
Change the top margin by editing the number--which is measured in inches--in the "Header from top" setting in the "Position" section on the Ribbon.
Change the bottom margin by editing the number--also measured in inches--in the "Header from bottom" setting in the "Position" section on the Ribbon.
Click "Page Layout" on the top of the program. The options in the "Page Layout" Ribbon lets you change the left and right indentations.
Change the left indent by editing the number in the "Left Indent" listing in the "Paragraph" section of the Ribbon.
Change the right indent by editing the number in the "Right Indent" listing in the "Paragraph" section of the Ribbon.
You can also press the up or down arrows next to the margin editing fields to change the margin 1/10 of an inch at a time. Change the entire document's page margins by clicking "Page Layout" and "Margins."