public void converttxttoPDF(string sourcePath, string destPath)
    {
        try
        {
            iTextSharp.text.Document document = new iTextSharp.text.Document();
            string filename = Path.GetFileNameWithoutExtension(sourcePath);
            System.IO.StreamReader myFile = new System.IO.StreamReader(sourcePath);
            string myString = myFile.ReadToEnd();
            myFile.Close();
            if (!Directory.Exists(destPath))
                Directory.CreateDirectory(destPath);
            iTextSharp.text.pdf.PdfWriter.GetInstance(document, new FileStream(destPath + "\" + filename + ".pdf", FileMode.CreateNew));
            document.Open();
            document.Add(new iTextSharp.text.Paragraph(myString));
            document.Close();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }

myString = string.IsNullOrEmpty(myString) ? " " : myString;
document.Add(new iTextSharp.text.Paragraph(myString));

Microsoft.Office.Interop.Word.Application word = new Microsoft.Office.Interop.Word.Application();
wordDocument = word.Documents.Open(savedFileName, ReadOnly: true);
wordDocument.ExportAsFixedFormat(attahcmentPath + "/pdf" + attachment.BetAttachmentCode + ".pdf", Microsoft.Office.Interop.Word.WdExportFormat.wdExportFormatPDF);
word.Quit(false);