Microsoft.Office.Interop.Word.Application winword = new Microsoft.Office.Interop.Word.Application();
Document document = winword.Documents.Open(@".docPath");
object filename = @"c:\temp1.docx";
document.SaveAs2(ref filename);
document.Close(ref missing, ref missing, ref missing);
document = null;
winword.Quit(ref missing, ref missing, ref missing);
winword = null;