Steps to reproduce: 
1. Set the main screen on 125-percent scale
2. Run attached sample application (1107416 RadPageView Issue.zip). 
3. Click menu item "ShowPageView". After showing the page view in a DocumentWindow, the SelectedPageChanging/SelectedPageChanged events are fired twice. 

Workaround: 
Replace RadPageView with custom one: 
public class CustomPageView : RadPageView
{
    protected override void ScaleControl(SizeF factor, BoundsSpecified specified)
    {
        this.SuspendEvents();
        base.ScaleControl(factor, specified);
        this.ResumeEvents();
    }
}