To zoom in a document, click the Zoom In button on the toolbar, or press CTRL+PLUS SIGN.
To zoom out of a document, click the Zoom Out button on the toolbar, or press CTRL+MINUS SIGN.
To zoom in or out of a document, you can also hold down CTRL and rotate the mouse wheel.
or Use the Magnifier Tool to switch between 100% and “fit whole page” views. Simply click anywhere in the document, to toggle views.