public Layout GetLayout()

{
  //Open a layout project item in a new view.
  //A layout project item may exist but it may not be open in a view. 

  //Reference a layout project item by name
  LayoutProjectItem layoutItemByName = Project.Current.GetItems<LayoutProjectItem>()
                            .FirstOrDefault(item => item.Name.Equals("MyLayoutItem"));

  //Get the layout associated with the layout project item
  //Note: Needs QueuedTask to run
  Layout layoutFromItem = layoutItemByName.GetLayout();  //Worker thread

  //Create the new pane - call on UI
  ILayoutPane iNewLayoutPane = await ProApp.Panes.CreateLayoutPaneAsync(layout); //GUI thread
}

{
  //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);
    }
  }
}