The sheet of paper drawn in the preview can not be centered or moved horizontally.
There is an option to turn the drawing of the sheet of paper off, so you have a complete white background. The property is named PaperView (DLL: use the function VpeSetPaperView()).
Thanks for the hint. I've tried it but it looks a bit confusing since you don't have a real impression of how it will look on the printed paper.
I think I leave the paper as it is. Having it centered would just be a nice "eye candy".