i have ude this code in my page .
page run but watermark is not added in pdf.
please help m.
my code

PdfReader pdfReader = new PdfReader(Server.MapPath("321.pdf"));
PdfStamper stamp = new PdfStamper(pdfReader, new System.IO.FileStream(Server.MapPath("watermark.pdf "), System.IO.FileMode.Create));

iTextSharp.text.Image img = iTextSharp.text.Image.GetInstance(Server.MapPath(" AIPL-watermark.jpg"));
img.SetAbsolutePosition(100, 100);

for (int j = 1; j < pdfReader.NumberOfPages; j++)
{
PdfContentByte waterMark = stamp.GetUnderContent(1);
waterMark.AddImage(img);
}
stamp.FormFlattening = true;
stamp.Close();
pdfReader.Close();