1 string sourceFileName = txtFileName.Text;
 2             string destFileName = Path.GetDirectoryName(sourceFileName) + @"\" + Path.GetFileNameWithoutExtension(sourceFileName) + "_带印章." + Path.GetExtension(sourceFileName);
 3             PdfDocument pdfDocument = new PdfDocument(new PdfReader(sourceFileName), new PdfWriter(destFileName));        
 4             iText.Layout.Document document = new iText.Layout.Document(pdfDocument);        
 5             ImageData imageData = ImageDataFactory.Create(System.Windows.Forms.Application.StartupPath + @"\PASS.png");
 6             for (int i = 1; i <= pdfDocument.GetNumberOfPages(); i++)
 7             {
 8                 iText.Layout.Element.Image image = new iText.Layout.Element.Image(imageData).ScaleAbsolute(55, 55).SetFixedPosition(i, 90, 50);
 9                 document.Add(image);
10             }
11             document.Close();