Please Try this.You may take some help from this.
RadDocument document = null;
IDocumentFormatProvider providerDocx = (IDocumentFormatProvider) new DocxFormatProvider();
using (FileStream stream = File.Open(@"C:\Test.docx", FileMode.Open))
{
document = providerDocx.Import(stream);
var providerPdf = new PdfFormatProvider();
Stream outStream = new MemoryStream();
providerPdf.Export(document, outStream);
//Test the conversion:
var fileStream = File.Create("PdfTest.pdf");
outStream.Seek(0, SeekOrigin.Begin);
outStream.CopyTo(fileStream);
fileStream.Close();
}