I want to add page number every page in export pdf

<pre> public byte[] GetPDF(string pHTML)
    {
        byte[] bPDF = null;

        MemoryStream ms = new MemoryStream();
        TextReader txtReader = new StringReader(pHTML);
       
        // we retrieve the total number of pages
        
        // 1: create object of a itextsharp document class
        Document doc = new Document(PageSize.LEGAL_LANDSCAPE, 10, 10, 42, 35);
        doc.SetPageSize(new Rectangle(850f, 1100f));
        // 2: we create a itextsharp pdfwriter that listens to the document and directs a XML-stream to a file
        PdfWriter oPdfWriter = PdfWriter.GetInstance(doc, ms);

        // 3: we create a worker parse the document
        HTMLWorker htmlWorker = new HTMLWorker(doc);
        
        // 4: we open document and start the worker on the document
        doc.Open();
        doc.NewPage();

        //htmlWorker.StartDocument();

        //// 5: parse the html into the document
        //htmlWorker.Parse(txtReader);
        List<IElement> elements = HTMLWorker.ParseToList(txtReader, null);
        foreach (IElement el in elements)
        {
            //If the element is a table manually set its header row count
            if (el is PdfPTable)
            {
                ((PdfPTable)el).HeaderRows = 2;

            }
            doc.Add(el);
        }
       

        // 6: close the document and the worker
        htmlWorker.EndDocument();
        htmlWorker.Close();
        doc.Close();

        bPDF = ms.ToArray();

        return bPDF;
    }

i want add page number every page in export pdf