code: public void drawForm (final PDFormXObject form) throws IOException
    {
      if (inTextMode)
      {
        throw new IllegalStateException ("Error: drawForm is not allowed within a text block.");
      }
  
      writeOperand (resources.add (form));
      writeOperator ((byte) 'D', (byte) 'o');
    }
docs: Draws the given Form XObject at the current location.
  
  @param form
  Form XObject
  @throws IOException
  if the content stream could not be written
  @throws IllegalStateException
  If the method was called within a text block.