How to convert.docs files to PDF programmatically in asp.net web application?

C# or .Net for that matter does not support any PDF conversion. You need to use third party components.

iTextSharp[^] is a free library which does it for you.

You can also use Aspose[^]. It's paid though.

If you have a MS 2007(with XPS and PDF addon) or MS2010, you can directly save the doc/docx files to pdf using the "SaveAs" method.

object filename = Path.GetTempPath() + @"\test.pdf";
                object fileFormat = WdSaveFormat.wdFormatPDF;

                oDoc.SaveAs(ref filename, ref fileFormat, ref oMissing, ref oMissing, ref oMissing, ref oMissing,
                             ref oMissing, ref oMissing, ref oMissing, ref oMissing, ref oMissing, ref oMissing,
                             ref oMissing, ref oMissing, ref oMissing);

                object save = false;
                oDoc.Close(ref save, oMissing, oMissing);