You can convert your html to pdf with itextsharp dll. Just make sure your html tags closed well.

htmlTopdf_itextsharp

// Namespaces
using System.IO;
using iTextSharp.text;
using iTextSharp.text.html.simpleparser;
using iTextSharp.text.pdf;
using iTextSharp.tool.xml;


// Lets consider your html looks like HTML.
string HTML = "<table style=\"width:800px;\"><tr><td style=\"width:100px;\">FOO</td><td style=\"width:10px\">:</td><td>BLABLABLA ...</td></tr></table>";
try
{
  //string filename = "\\pdf\\x_pdf___" + Request.QueryString["id"] + ".pdf";
	string filepath = HttpContext.Current.Server.MapPath("\\pdf\\x_pdf___" + Request.QueryString["id"] + ".pdf");
	Document document = new Document(PageSize.A4);
	PdfWriter writer = PdfWriter.GetInstance(document, new FileStream(filepath, FileMode.Create));
	document.Open();
	HTMLWorker hw = new HTMLWorker(document);
	StringReader sr = new StringReader(HTML);
	XMLWorkerHelper.GetInstance().ParseXHtml(writer, document, sr);
	//hw.Parse(new StringReader(HTML));
	document.Close();
	ShowPdf(filename, filepath);
	PdfAction action = new PdfAction(PdfAction.PRINTDIALOG);
}
catch (Exception ex)
{
	string error = ex.Message;
}

// function to show on page
private void ShowPdf(string filename, string filePath)
{
	Response.ClearContent();
	Response.ClearHeaders();
	Response.ContentType = "application/pdf";
	Response.BufferOutput = true;
	string FilePath = HttpContext.Current.Server.MapPath(filename);
	Response.WriteFile(FilePath);
	Response.End();
}

iTextSharp.text.Image addLogo = default(iTextSharp.text.Image);
addLogo = iTextSharp.text.Image.GetInstance(Server.MapPath("Images") + "/Content/images/asia-cloud-logo.png");
addLogo.SetAbsolutePosition(30f, 800f);
addLogo.ScaleToFit(128, 37);

your other code
document.Open();
HTMLWorker hw = new HTMLWorker(document);

            StringReader sr = new StringReader(xx.ToString());
            document.Add(addLogo);