Here is how did using an opesource library called IText. I have taken the code of exporting the charts to image for this forum and modified it to get the image as PDF using IText.

www.lowagie.com/iText/

This is a working code. Create a servlet add this POST method to it and you are done.

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
         String heightStr = request.getParameter("height")==null?"0":request.getParameter("height");
         String widthStr = request.getParameter("width")==null?"0":request.getParameter("width");
         int height=Integer.parseInt(heightStr.indexOf(".")==-1?heightStr:heightStr.substring(0,heightStr.indexOf(".")));
         int width=Integer.parseInt(widthStr.indexOf(".")==-1?widthStr:widthStr.substring(0,widthStr.indexOf(".")));
         BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
         Graphics g = image.getGraphics();
         
         String current_row="";
         Image docImage=null;
         try{
             for(int i=0;i<height;i++){
                 current_row=request.getParameter("r"+i)==null?"":request.getParameter("r"+i);
                 String current_col[]=current_row.split(",");
                 int current_width=1;
                 for(int m=0;m<current_col.length;m++){
                     String pixel[]=current_col[m].split(":");
                     
                     if(pixel.length>1){
                         g.setColor(this.charColor(pixel[0]));
                         g.drawLine(current_width, i, current_width+Integer.parseInt(pixel[1]), i);
                         current_width=current_width+Integer.parseInt(pixel[1]);
                     }else if(pixel.length==1){
                         g.setColor(this.charColor(pixel[0]));
                         g.drawLine(current_width, i, current_width+1, i);
                         current_width++;
                     }
                     
                     
                 }
             }
             
         docImage   = Image.getInstance(image, null);
             
         }catch(Exception e){
             e.printStackTrace();
         }   
         g.create();
         
        Document doc = new Document();
        ByteArrayOutputStream baosPDF = new ByteArrayOutputStream();
        PdfWriter docWriter = null;
        try {
            docWriter = PdfWriter.getInstance(doc, baosPDF);
            doc.open();
           
            Table table = new Table(1, 1);
            table.setWidth(100);
            table.setTableFitsPage(true);
            table.setAlignment(Table.ALIGN_LEFT);
            table.setBorder(Table.NO_BORDER);

            Cell cell = new Cell();
            cell.setBorder(Cell.NO_BORDER);
            cell.setVerticalAlignment(Cell.ALIGN_TOP);
            cell.add(docImage);
           
            table.addCell(cell);
            doc.add(table);

            doc.close();

        } catch (DocumentException e) {
            e.printStackTrace();
        }
        response.setContentType("application/pdf");
        response.setContentLength(baosPDF.size());
        ServletOutputStream out = response.getOutputStream();
        baosPDF.writeTo(out);
        out.flush();
       
     }
     
     
     public Color charColor(String hex){
         for(int i=0;i<6;i++){
             if(hex.length()<6)hex="0"+hex;
         }
         int r=this.HtoD(hex.substring(0,2));
         int g=this.HtoD(hex.substring(2,4));
         int b=this.HtoD(hex.substring(4,6));
         
         Color color = new Color(r,g,b);
         return color;
     }
     
     public int HtoD(String hex){
         return Integer.valueOf(hex, 16);
     }

------------------ at JSP/Html end add this JS--------------------------------------------:
  function exportColumnPDF()
{
      flashMovie = document.getElementById("amcolumn");
      flashMovie.exportImage('/webapp/Export'); // it is not required to pass filename here if you set it in settings file)
}
and call this method against your chart. In this case am using it for my columnchart i.e. "amcolumn"
/Export is my servlet name in web.xml
-----------------------------------------------------------------------------------------------

Enjoy :) !!!
Thanks & Regards,
Kapil