Click the Page Layout tab.
Click the Size button from the submenu.
The current margin setting is highlighted on the submenu.
Click Letter (8.5 x 11), Letter Small (8.5 x 11), Tabloid (11 x 17), Ledger (17 x 11, Legal (8.5 x 14), Statement (5.5 x 8.5), Executive (7.25 x 10.5), A3 (11.69 x 16.54), A4 (8.27 x 11.69), A4 Small (8.27 x 11.69) from the submenu.