Problem with internet explorer and special characters

Hi, i’m triying to generate a pdf file from a servlet (a filter-servlet to be specific) the thing is that the html that i’m trying to convert have special characters (á é í ó ú ñ) but they are all in the ISO-8859-1 encoding, when i open the URL with firefox all works ok but when i try to open the url with IE the special characters does not render ok, this is my code:

//the important part of the code
PD4ML pd4ml = new PD4ML();

pd4ml.setPageInsets(new Insets(20, 10, 10, 10));
pd4ml.setHtmlWidth(800);
pd4ml.setPageSize(pd4ml.changePageOrientation(PD4Constants.LETTER));

response.setContentType("application/pdf");
response.setCharacterEncoding("ISO-8859-1");
pd4ml.enableDebugInfo();
ByteArrayOutputStream salida = new ByteArrayOutputStream();

pd4ml.render(new StringReader(preProcessPage), salida ,new URL("http://"+
request.getServerName()+":"+request.getLocalPort()+
this.getFilterConfig().getServletContext().getContextPath()),"ISO-8859-1");

response.setContentLength(salida.size());

response.getOutputStream().write(salida.toByteArray());
response.getOutputStream().close();

//more code

The weird thing is that the code works perfect in firefox, maybe the problem is the internet explorer or the pdf plugin, any ideas? thanks….