@Babiker Assie To add to the great answer that IM provided, here is a sample by using iTextSharp to convert an ASPX page to a PDF:
using iTextSharp.text;
using iTextSharp.text.pdf;
using System.IO;
using System.Net;
// Get the ASPX page content
string url = "http://example.com/mypage.aspx";
WebClient client = new WebClient();
string html = client.DownloadString(url);
// Convert the HTML to PDF
Document document = new Document();
PdfWriter.GetInstance(document, new FileStream("mypage.pdf", FileMode.Create));
document.Open();
HTMLWorker worker = new HTMLWorker(document);
worker.Parse(new StringReader(html));
document.Close();
Let us know if you have any further questions.