使用iTextSharp在多个导入的PDF页面上放置文本

Question

大家好，感谢您的帮助。我正在尝试创建一个Web应用程序，利用iTextSharp导入多页pdf，不同页面上的地方文本，换句话说，第1页的某个文本，页面的不同文本等等。我已经成功了导入pdf，但文本正在逃避我。这是我的代码：

            PdfReader reader = null;
        Document sourceDocument = null;
        PdfCopy pdfCopyProvider = null;
        PdfImportedPage importedPage = null;

        int startPage = 1;
        int endPage = 2;

        try
        {

            string sourcePdfPath = Server.MapPath(path);
            // Intialize a new PdfReader instance with the contents of the source Pdf file:
            reader = new PdfReader(sourcePdfPath);

            // For simplicity, I am assuming all the pages share the same size
            // and rotation as the first page:
            sourceDocument = new Document(reader.GetPageSizeWithRotation(startPage));

            // Initialize an instance of the PdfCopyClass with the source 
            // document and an output file stream:
            //
            MemoryStream ms = new MemoryStream();
            pdfCopyProvider = new PdfCopy(sourceDocument, ms);
            //
            //pdfCopyProvider = new PdfCopy(sourceDocument,
            //    new System.IO.FileStream(outputPdfPath, System.IO.FileMode.Create));

            sourceDocument.Open();

            // Walk the specified range and add the page copies to the output file:
            for (int i = startPage; i <= endPage; i++)
            {
                importedPage = pdfCopyProvider.GetImportedPage(reader, i);
                pdfCopyProvider.AddPage(importedPage);
            }

            PdfContentByte cb = pdfCopyProvider.DirectContent;

        PdfReader reader = null;
        Document sourceDocument = null;
        PdfCopy pdfCopyProvider = null;
        PdfImportedPage importedPage = null;

        int startPage = 1;
        int endPage = 2;



        try
        {

            string sourcePdfPath = Server.MapPath(path);
            // Intialize a new PdfReader instance with the contents of the source Pdf file:
            reader = new PdfReader(sourcePdfPath);

            // For simplicity, I am assuming all the pages share the same size
            // and rotation as the first page:
            sourceDocument = new Document(reader.GetPageSizeWithRotation(startPage));

            // Initialize an instance of the PdfCopyClass with the source 
            // document and an output file stream:
            //
            MemoryStream ms = new MemoryStream();
            pdfCopyProvider = new PdfCopy(sourceDocument, ms);
            //
            //pdfCopyProvider = new PdfCopy(sourceDocument,
            //    new System.IO.FileStream(outputPdfPath, System.IO.FileMode.Create));

            sourceDocument.Open();

            // Walk the specified range and add the page copies to the output file:
            for (int i = startPage; i <= endPage; i++)
            {
                importedPage = pdfCopyProvider.GetImportedPage(reader, i);
                pdfCopyProvider.AddPage(importedPage);
            }

            PdfContentByte cb = pdfCopyProvider.DirectContent;

            //select the font properties 
            BaseFont bf = BaseFont.CreateFont(BaseFont.HELVETICA, BaseFont.CP1252, BaseFont.NOT_EMBEDDED);
            cb.SetColorFill(BaseColor.DARK_GRAY);
            cb.SetFontAndSize(bf, 12);

            //write the Patient Name
            cb.BeginText();
            //put the alignment and coordinates here 
            cb.ShowTextAligned(3, "Hello", 200, 200, 0);
            cb.EndText();

            sourceDocument.Close();
            reader.Close();

            Response.ContentType = "application/pdf";
            Response.AddHeader("content-disposition", "attachment;filename=file.pdf");
            Response.Buffer = true;
            Response.Clear();
            Response.OutputStream.Write(ms.GetBuffer(), 0, ms.GetBuffer().Length);
            Response.OutputStream.Flush();
            Response.End();
        }
        catch (Exception ex)
        {
            throw ex;
        }


    }

            sourceDocument.Close();
            reader.Close();

            Response.ContentType = "application/pdf";
            Response.AddHeader("content-disposition", "attachment;filename=file.pdf");
            Response.Buffer = true;
            Response.Clear();
            Response.OutputStream.Write(ms.GetBuffer(), 0, ms.GetBuffer().Length);
            Response.OutputStream.Flush();
            Response.End();
        }
        catch (Exception ex)
        {
            throw ex;
        }


    }

任何帮助都将不胜感激。