This command enables or disables automatic zooming. If enabled, PMView zooms the image according to the criteria set on the View page in PMView's preferences notebook. If disabled, the image is not zoomed. Note that manual zooming always takes precedence over this setting. If the image is manually zoomed when changing this setting, nothing will happen. However, as soon as you exit manual zoom with Zoom Off, this setting will be effective again.
The shortcut key for Zoom to Fit is Ctrl+F.