regarding .pdf generation from web form

Hi,

        I am created a Order Form for my customers. Whichever order they give us I read it and generate a quotation for them. We have a standard layout for quotation. I made it as it is. Now i want to export it in .pdf file. 

       I read your artical : http://www.aspsnippets.com/Articles/Export-ASPNet-Web-Page-with-images-to-PDF-using-ITextsharp.aspx. which not running on my web site [But as it is ran.] Please help to run this portion.

Error : 

Object reference not set to an instance of an object.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.  Exception Details: System.NullReferenceException: Object reference not set to an instance of an object. Source Error: 

Line 185:        PdfWriter.GetInstance(pdfDoc, Response.OutputStream);
Line 186:        pdfDoc.Open();
Line 187: htmlparser.Parse(sr); Line 188:        
Line 189:        pdfDoc.Close();

Thanks.