You can implement it with the extra prevnextPage. However, you have to remove some spaces in the snippet in line 51 or 65, otherwise you will get an error message (tested with EVO 3.1.8).
Line 51 from:
$docs = $modx->getDocumentChildren ($folderId, 1, 0, 'id, pagetitle, parent', 'hidemenu = '.$showHidden, $sortBy, $sortDir, '');
to:
$docs = $modx->getDocumentChildren ($folderId, 1, 0, 'id,pagetitle,parent', 'hidemenu = '.$showHidden, $sortBy, $sortDir, '');