Microsoft Word's default page size is 8.5 inches by 11 inches, but you can change the page size of any document manually or by using one of Word's built-in templates. Enlarging a page in Microsoft Word may be necessary if you find that your document proves wider or bigger than originally imagined or if you have a specific paper size or space to fit.
Open Word and click the “File” tab. Click “Open.” Click “Browse.” Locate the document with the pages you wish to enlarge and double-click on the file name, which opens the document in a new Word window.
Click the “Page Layout” tab at the top of the work area. Click the “Size” button directly below the tab.
Select one of the new, pre-set larger page sizes or click “More Paper Sizes” to create a customized paper size. Word automatically resizes the pages of the document to fit the new size.