Issue using StringReader in CRM Online Plugin

Hi,

We are generating a PDF file using iTextSharp Assembly. But CRM is throwing error in below line

HTMLWorker hw = new iTextSharp.text.html.simpleparser.HTMLWorker(document);

  hw.Parse(new StreamReader(html));

html is the HTML string. The error we get is "Request for the permission of type 'System.Security.Permissions.EnvironmentPermission, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed". I checked and found that usage of StringReader is not allowed due to security reasons. Can someone help us out here?