By default, the image displayed is the bitmap stored with the SolidWorks file. Toolbar buttons let you zoom in and out and pan the image.

If SolidWorks eDrawings is installed, you can switch to eDrawings mode by clicking eDrawings
on the toolbar or expanding the action menu to the left of the Preview tab and selecting Show eDrawings for SolidWorks files.

SolidWorks eDrawings Controls
When eDrawings is selected as the Preview mode, the toolbar contains an extended set of controls.
