VIEWCTL is your new friend. This works in progeCAD 2009 as follows:
1) Switch to paperspace / layout tab for the current DWG drawing file (yeah...)
2) Make sure you are editing within the viewport you want to rotate the view of. You can do this by double left clicking on any geometry within the target floating viewport (mview). Note: by defaults the visible border around the viewport should darken when you do this to indicate the active viewport.
3) Type VIEWCTL (or from Menu: "View" -> "3D Views" -> "View Control"). A control panel will appear as shown:
A little tour of the VIEWCTL control panel - the upper left previews the view relative to WCS using the picture of a simple 3D axis. Six icons to the upper right are like "dials" allowing you to turn the viewpoint around the axis indicated by the black line in the middle of each icon. Each time you click on a "turn" the preview will "rotate" in degree increments specified in the "Change By" field. Click "OK" to apply the view rotation.
For your case, you can edit the "Change By" value to 90 (degrees) and click once the lower right "dial" which represents clockwise view turn about Z axis (if your view is TOP which is default view)
Sounds a bit elusive but it really isn't. Best is try it a few times on your own - I'm sure you can get the hang of it. Also you can undo these changes in progeCAD if you decide later. There are a couple of other ways to manage this in progeCAD as well, BTW.
progeCAD support, tips and troubleshooting forum. progeCAD works very similar to some versions of AutoCAD. Moderated.