using ...
using Word = Microsoft.Office.Interop.Word;

public bool Traite_Word(string sFile)
        {
            Word.Application word = null;
            Word.Document doc = null;
            bool bRet = false;
            string sOut = string.Empty;


            if (!File.Exists(sFile))
                return false;
            FileInfo fi = new FileInfo(sFile);
            sOut = fi.FullName.Replace(fi.Extension, ".pdf");

            try
            {
                word = new Word.Application();
                word.Visible = false;
                doc = word.Documents.Open(sFile);
                doc.Activate();
                doc.SaveAs2(sOut, Word.WdSaveFormat.wdFormatPDF);
                doc.Close();
                word.Quit();
                bRet = true;

            }
            catch (Exception ex)
            {                
                LogEvent(sMess);             
            }
            return bRet;
        }