MapViewer 8 added the ability to make the zoom commands stay available. The zoom command buttons on the View tab are now multi-use instances. After clicking the command, click on the plot window where you want to zoom. The display updates and the command stays activated. Click again on the plot window to zoom again. When you have the zoom at the desired level, click the View zoom command again to deactivate it or press the ESC key on the keyboard.
The mouse wheel can also be used. Rotate the mouse wheel forward to zoom in, rotate the mouse wheel backward to zoom out. Press and hold the mouse wheel down to pan the view.
In older versions of MapViewer (4-7), you can zoom continuously by double clicking on the zoom tool to enable persistent draw mode, clicking on your page the number of times you want to zoom in or out, then pressing ESC on your keyboard to exit the persistent draw mode. Alternatively, you can click View | Zoom | Zoom Realtime, then click and drag your mouse up on the page to zoom in or down on the page to zoom out.
Updated July 31, 2018