If you're writing a document you want to fit on a single page, but changing the text size would make it too hard to read, try adjusting the margins to see if that will do the trick. (The margin are the blank space around the edges of the text and images on a page.)
Watch these helpful video tutorials to learn how to adjust margins, depending on the version of Microsoft Word that you use:
- Word 2003: http://office.microsoft.com/en-us/word-help/change-page-margins-RZ010014036.aspx?section=8
- Word 2007: http://office.microsoft.com/en-us/word-help/change-page-margins-RZ010227511.aspx?section=6
- Word 2010: http://office.microsoft.com/en-us/word-help/change-margins-RZ101790574.aspx?section=7