1. Insert > Header > Edit Header
2. Type your text for the header.
3. Select all the text you just typed and right-click on it.
4. Click on the Home tab.
5. Click on the little window button for borders.
6. Select the bottom border you want. It should be for the paragraph.
7. Scroll down to the footer area and do the same except use a top border.

Sections / Headers and Footers in Microsoft Word 2007-2013