public CIMPage GetPage()

{
  //Change the layout page size.
  //Reference the layout project item
  LayoutProjectItem lytItem = Project.Current.GetItems<LayoutProjectItem>()
                         .FirstOrDefault(item => item.Name.Equals("MyLayoutItem"));
  if (layoutItem != null)
  {
    //Note: Needs QueuedTask to run
    //Get the layout
    Layout lyt = lytItem.GetLayout();
    if (lyt != null)
    {
      //Change properties
      CIMPage page = lyt.GetPage();
      page.Width = 8.5;
      page.Height = 11;

      //Apply the changes to the layout
      lyt.SetPage(page);
    }
  }
}