If you open a SketchUp file, or any 3D file for that matter, and prefer to see it in hidden line mode, in Model Space you can select View - Visual Styles - Hidden Line.
If you are in a paper space, double click on the viewport (or in the context menu select Properties). From the Properties menu under Render Styles select Hidden Line view.
If you have a Top or Side view in paper space that you want to dimension, double click on the viewport to open Properties, select Camera, then deselect "Perspective View" to turn it off. Because this change is actually being made by "editing" the view in paper space it may reset the scale. If so, go to Modify and select Space Change. Then click once on the middle mouse button (to zoom extents in the viewport). Then click outside of the viewport to deselect it.