code: public void replacePage(PdfReader r, int pageImported, int pageReplaced) {
          stamper.replacePage(r, pageImported, pageReplaced);
      }
docs: Replaces a page from this document with a page from other document. Only the content
  is replaced not the fields and annotations. This method must be called before
  getOverContent() or getUndercontent() are called for the same page.
  @param r the <CODE>PdfReader</CODE> from where the new page will be imported
  @param pageImported the page number of the imported page
  @param pageReplaced the page to replace in this document
  @since iText 2.1.1