if i just change Landscape propery page preview doesnt change pages layout.
There is no property notification that occurs when you change those properties so you must manually invalidate the preview. You can either call the InvalidatePreview method on the UltraPrintPreviewDialog or the InvalidatePreview method of the UltraPrintPreviewControl within it.
Thanks
While waiting i found out it also works if you reassign Dialogs document
P.S. Although its good to know the way it should be done :)