You can place a page break using one of the CSS properties "page-break-before: always;" or "page-break-after: always;". The former property will always cause a page break before the element it is applied to, while the latter will cause it after the element. For example, this code will enforce a page break after the div with the class selector "1", no matter if one is required or not:

div.1 { page-break-after: always; }

For further reference, please see the chapter Page Breaks in the PDFreactor manual.