How to merge pdf files from SQL database

<pre> private void DocumentFile()
        {
           
            Document document = new Document();
             DataTable dTable = document.GetDocuments();
            if (dTable.Rows.Count > 0)
            {
                foreach (DataRow row in dTable.Rows)
                {
                    string contentType = dTable.Rows[0]["ContentType"].ToString();
                    string extension = dTable.Rows[0]["Extension"].ToString();
                    byte[] content = (byte[])dTable.Rows[0]["Content"];
                    Response.Clear();
                    MemoryStream ms = new MemoryStream(content);
                    Response.ContentType = contentType;
                    Response.AddHeader("Content-Disposition", "attachment; filename=\""
                        + "Doc" + extension + "\"");
                    Response.Buffer = true;
                    ms.WriteTo(Response.OutputStream);
                  
                }
            }

        }