why pdfstamper is not working to insert new buttons in itextpf

Question

I just copied a program from website (I am sure it was written by Bruno) but does not work for me. I just have a very plain pdf fie and interested to insert buttons in it using this program exactly. But it does not insert the button on the file. My original file is in "/WEB-INF/design100.pdf".

  package admin_pack;

 import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Set;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Rectangle;
import com.itextpdf.text.pdf.AcroFields;
import com.itextpdf.text.pdf.GrayColor;
import com.itextpdf.text.pdf.PdfAction;
import com.itextpdf.text.pdf.PdfFormField;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfStamper;
import com.itextpdf.text.pdf.PushbuttonField;
import com.itextpdf.text.pdf.TextField;
import javax.servlet.annotation.WebServlet;

/**
 *
 * @author Mushtaq
 */
@WebServlet(name = "FormServlet", urlPatterns = {"/FormServlet"})
public class FormServlet extends HttpServlet {

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("application/pdf");
        try {
            // We get a resource from our web app
            InputStream is
                    = getServletContext().getResourceAsStream("/WEB-INF/design100.pdf");
            // We create a reader with the InputStream
            PdfReader reader = new PdfReader(is, null);
            // We create an OutputStream for the new PDF
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            // Now we create the PDF
            PdfStamper stamper = new PdfStamper(reader, baos);

            // We add a submit button to the existing form
            PushbuttonField button = new PushbuttonField(
                    stamper.getWriter(), new Rectangle(90, 660, 140, 690), "submit");
            button.setText("POST");
            button.setBackgroundColor(new GrayColor(0.7f));
            button.setVisibility(PushbuttonField.VISIBLE_BUT_DOES_NOT_PRINT);
            PdfFormField submit = button.getField();
       //     submit.setAction(PdfAction.createSubmitForm(
            //        "/book/form", null, PdfAction.SUBMIT_HTML_FORMAT));
            stamper.addAnnotation(submit, 1);
            stamper.close();
            reader.close();
            // We write the PDF bytes to the OutputStream
            OutputStream os = response.getOutputStream();
            baos.writeTo(os);
            os.flush();
        } catch (DocumentException e) {
            throw new IOException(e.getMessage());
        }
    }

}