The ZoomIn method increases the zoom level for the current
document.
Changing the zoom level affects how the page content is displayed
but does not alter the underlying document. This is equivalent to
adjusting the zoom in a standard web browser. The new zoom level
applies to the current browser instance and will remain in effect
until it is changed again, or the control is destroyed.
The value of the AllowZoom property does not affect your
ability to change the zoom level using this method. The ZoomLevel
property can be used to set the view to a specific percentage value.