private void CurrentPageSelectButton_Click(object sender, RoutedEventArgs e)
        {
            ToggleButton button = sender as ToggleButton;

            if (button.IsChecked ?? false)
            {
                selectedPageRange.Add((int)renderedPageNumber);
            }
            else
            {
                selectedPageRange.Remove((int)renderedPageNumber);
            }
            PageRangeInput.Text = selectedPageRange.ToString();
            ShowSummary();
        }