使用itextsharp从ftp下载（流式传输）时添加文本pdf

Question

我有一些代码用于在浏览器中显示来自ftp的pdf文件。我必须为来自ftp的pdf添加一些文本。我从antoher项目中找到了一些工作代码，但它从iis本地路径写入pdf。

//** these are my working code that show pdf files in browser from ftp. **//
    string filename = Request.QueryString["view"];           
    string ftpServerIP = Session["Host"].ToString();
    string ftpUserName = Session["user"].ToString();
    string ftpPassword = Session["pssw"].ToString();
    FileInfo objFile = new FileInfo(filename);

    System.Net.FtpWebRequest request = (System.Net.FtpWebRequest)WebRequest.Create(new Uri("ftp://" + ftpServerIP + "/" + objFile.Name));
    request.Credentials = new NetworkCredential(SftpUserName, ftpPassword);

    request.Method = WebRequestMethods.Ftp.GetFileSize;
    System.Net.FtpWebResponse response = (System.Net.FtpWebResponse)request.GetResponse();
    int length = (int)(response.ContentLength * 1.1);

    request = (System.Net.FtpWebRequest)WebRequest.Create(new Uri("ftp://" + ftpServerIP + "/" + objFile.Name));
    request.Credentials = new NetworkCredential(ftpUserName, ftpPassword);

    request.Method = WebRequestMethods.Ftp.DownloadFile;
    response = (System.Net.FtpWebResponse)request.GetResponse();

    Stream responseStream = response.GetResponseStream();
    StreamReader reader = new StreamReader(responseStream);

    BinaryReader br = new BinaryReader(responseStream);
    byte[] buffer = br.ReadBytes(length);
    //** Can I work the itextsharp codes near here for adding text, without saving local, before download? **//
    Response.Clear();
    Response.ClearHeaders();
    Response.ClearContent();
    Response.ContentEncoding = reader.CurrentEncoding;
    Response.ContentType = "application/pdf";
    Response.AddHeader("Content-Disposition", "inline; filename=" + Request.QueryString["name"]);
    Response.BinaryWrite(buffer);


//** these are another code which I need to implement my code for adding some text in pdf files.**//
//** these are not my actual codes, just from another project's and I have to use them in my project.**//
//** The difference is in my project download pdf directly from an ftp, other one reads pdf in local files.**//


    private void WriteToPdf(FileInfo sourceFile, string outbut_File, string stringToWriteToPdf)
    {
        PdfReader reader = new PdfReader(sourceFile.FullName);


        PdfStamper pdfStamper = new PdfStamper(reader, new System.IO.FileStream(outbut_File, FileMode.Create, FileAccess.Write, FileShare.Write));

        iTextSharp.text.pdf.PdfGState Gstates = new iTextSharp.text.pdf.PdfGState();
        Gstates.StrokeOpacity = 0.3f;
        Gstates.FillOpacity = 0.3f;

        for (int i = 1; i <= reader.NumberOfPages; i++)
        {    
            iTextSharp.text.Rectangle pageSize = reader.GetPageSizeWithRotation(i);

            PdfContentByte pdfPageContents = pdfStamper.GetOverContent(i);
            pdfPageContents.BeginText();

            BaseFont baseFont__1 = BaseFont.CreateFont(BaseFont.HELVETICA_BOLD, BaseFont.WINANSI, BaseFont.NOT_EMBEDDED);
            //BaseFont.CreateFont("", BaseFont.WINANSI, BaseFont.NOT_EMBEDDED)
            pdfPageContents.SetFontAndSize(baseFont__1, 15);
            pdfPageContents.SetRGBColorFill(255, 0, 0);
            pdfPageContents.SaveState();
            float textAngle = 0;
            pdfPageContents.ShowTextAligned(PdfContentByte.ALIGN_LEFT, stringToWriteToPdf, 5, 5, textAngle);
            pdfPageContents.ShowTextAligned(PdfContentByte.ALIGN_LEFT, stringToWriteToPdf, pageSize.Width, pageSize.Height, textAngle);

            pdfPageContents.EndText();
        }

        pdfStamper.FormFlattening = true; 
        pdfStamper.Close();
        reader.Close();
        Stream s = File.OpenRead(outbut_File);
        byte[] buffer = new byte[s.Length + 1];
        try
        {
            s.Read(buffer, 0, (Int32)s.Length);
        }
        finally
        {
            s.Close();
        }
        Response.ClearContent();
        Response.ContentType = "application/pdf";
        Response.AddHeader("Content-Disposition", "inline; filename=" +  Request.QueryString["name"]);
        Response.WriteFile(outbut_File);
        Response.End();
    }

如何通过下载ftp并添加文本然后在浏览器中显示来自定义这些代码？