wp_link_pages( array(
    'before'      => '<div class="page-links"><span class="page-links-title">' . __( '', 'twentyfourteen' ) . '</span>',
    'after'       => '</div>',
  'nextpagelink' => __('<b>Next</b> <i class="fa fa-arrow-right" aria-hidden="true"></i>'),
  'previouspagelink' => __('<i class="fa fa-angle-left" aria-hidden="true"></i> Next '),
    'link_before' => ' <div class="btn btn-default" >',
    'link_after'  => '</div>',
  'next_or_number'   => 'next'

    ) );