public class Watermark extends PdfPageEventHelper {
 
        protected Phrase watermark = new Phrase("WATERMARK", new Font(FontFamily.HELVETICA, 60, Font.NORMAL, BaseColor.LIGHT_GRAY));
 
        @Override
        public void onEndPage(PdfWriter writer, Document document) {
            PdfContentByte canvas =
 
 writer.getDirectContentUnder();
            ColumnText.showTextAligned(canvas, Element.ALIGN_CENTER, watermark, 298, 421, 45);
        }
    }

public void createPdf(String dest) throws IOException, DocumentException {
        Document document = new Document();
        PdfWriter writer = PdfWriter.getInstance
 
(document, new FileOutputStream(dest));
        writer.setPageEvent(new Watermark());
        document.open();
//--------

                document.close();
    }