How to add a Watermark below the graphics and text in the existing WF PDF?

//Loads the pdf document
PdfLoadedDocument ldoc = new PdfLoadedDocument("Bullets and Lists.pdf");
//Creats new pdf document
PdfDocument doc = new PdfDocument();
//itereate through the pages of loaded document
foreach (PdfLoadedPage lpage in ldoc.Pages)
{
//Adds new Page
PdfPage page = doc.Pages.Add();
//Create template from the loaded page
PdfTemplate template = lpage.CreateTemplate();
//Method for drawing Watermark from newly created pdf document page
DrawWatermark(page);
//Draws template of loaded page from pdf document page.
page.Graphics.DrawPdfTemplate(template, PointF.Empty);
}
//Save the document and dispose it
doc.Save("Loaded.pdf", Response, HttpReadType.Save);
doc.Close();
}
private void DrawWatermark(PdfPage page)
{
// Sets font
PdfFont bigFont = new PdfStandardFont(PdfFontFamily.Helvetica, 80f);
string s = "WaterMark";
//Saves the graphics state
PdfGraphicsState state = page.Graphics.Save();
//Measures the size of the string
 SizeF textSize = bigFont.MeasureString(s);
//The Translate transform changes the origin of the coordinate system by prepending the specified translation to the transformation matrix of this Graphics.
page.Graphics.TranslateTransform((page.Size.Width/2)-200,page.Size.Height/2+100);
//Applying rotation for watermark
page.Graphics.RotateTransform(-45);
//Sets transparency
page.Graphics.SetTransparency(0.4f);
//Draw string
page.Graphics.DrawString(s, bigFont, PdfPens.Gray, PdfBrushes.LightGray, new PointF(0, 0));
//Restores the graphics state
page.Graphics.Restore(state);
 }