I need to cross out the empty space on the last page

procedure TForm1.WPRichText1PaintWatermark(Sender: TObject;
  RTFEngine: TWPRTFEnginePaint; toCanvas: TCanvas; PageRect: TRect;
  PaintPageNr, RTFPageNr: Integer; WaterMarkRef: TObject; XRes,
  YRes: Integer; CurrentZoom: Single; PaintMode: TWPPaintModes);
begin
  if RTFPageNr=WPRichText1.PageCount then
  begin
     toCanvas.Pen.Style := psSolid;
     toCanvas.Pen.Width := MulDiv(15,XRes,1440);
     toCanvas.Pen.Color := clBlack;
     toCanvas.MoveTo(PageRect.Left, PageRect.Top +
       MulDiv(WPRichText1.Memo.PaintPageTextHeight[PaintPageNr],
          YRes, WPScreenPixelsPerInch) +
       WPRichText1.BodyText.Pages[RTFPageNr-1].MarginTop
        );
     toCanvas.LineTo(PageRect.Right, PageRect.Bottom);  
  end;
end;

var xx, xx1, yy, yy1 : Integer;
begin
  if RTFPageNr=WPRichText1.PageCount then
  begin
     toCanvas.Pen.Style := psSolid;
     toCanvas.Pen.Width := MulDiv(15,XRes,1440);
     toCanvas.Pen.Color := clBlack;


     xx  := PageRect.Left + MulDiv(WPRichText1.Header.LeftMargin,xres,1440);
     xx1 := PageRect.Right - MulDiv(WPRichText1.Header.RightMargin,xres,1440);
     yy  := PageRect.Top + MulDiv(WPRichText1.Memo.PaintPageTextHeight[PaintPageNr],
          YRes, WPScreenPixelsPerInch) +
          WPRichText1.BodyText.Pages[RTFPageNr-1].MarginTop;
     yy1 := PageRect.Bottom- WPRichText1.BodyText.Pages[RTFPageNr-1].MarginBottom;


     toCanvas.MoveTo(xx,yy);
     toCanvas.LineTo(xx + ((xx1-xx)div 3), yy);
     toCanvas.LineTo(xx + ((xx1-xx)div 3)*2, yy1);
     toCanvas.LineTo(xx1, yy1);
  end;