public class PageEvents : PdfPageEventHelper

{

        PdfTemplate _backgroundImageTemplate;



        public override void OnStartPage(PdfWriter writer, Document document)

        {

            base.OnStartPage(writer, document);

            writer.DirectContent.AddTemplate(_backgroundImageTemplate, 0, 0);

        }



        public override void OnOpenDocument(PdfWriter writer, Document document)

        {

            _backgroundImageTemplate = writer.DirectContent.CreateTemplate(document.PageSize.Width, document.PageSize.Height);

        }



        public override void OnCloseDocument(PdfWriter writer, Document document)

        {

            base.OnCloseDocument(writer, document);



            iTextSharp.text.Image img = iTextSharp.text.Image.GetInstance(

			@"C:\My Pictures\bg.png");

            img.Alignment = iTextSharp.text.Image.UNDERLYING;

            img.SetAbsolutePosition((document.PageSize.Width - img.Width) / 2, (document.PageSize.Height - img.Height) / 2);

            _backgroundImageTemplate.AddImage(img);

        }

}