This depends a bit on what you would expect to happen as you change the zoom.
The layout you're describing can be achieved by setting the horizontal alignment to left (PDFViewWPF.SetHorizontalAlign(-1)) and then finding an appropriate zoom level.
However, when you zoom in, it will take up the gray space you have indicated.
We currently do not have a way to display a PDF with a specific amount of gray space only to the right of the document.
You could try to use void SetPageSpacing(int horizSpace, int vertSpace, int horizPad, int vertPad);
though that will leave blank space both left and right of the page.
Finally, you could try to create a custom control.
For example, if this control has it's own scroll viewer that is bound to the one of the PDFViewWPF, you might be able to hide the ScrollBar of the PDFViewWPF.