code: public void add(PdfContentByte other) {
          if (other.writer != null && writer != other.writer)
              throw new RuntimeException("Inconsistent writers. Are you mixing two documents?");
          content.append(other.content);
      }
docs: Adds the content of another <CODE>PdfContent</CODE>-object to this object.
  
  @param       other       another <CODE>PdfByteContent</CODE>-object