You could do it by
=> Using strpos() to detect the position of a whitespace in your text near the position that you would like to split:
// set length of page
$pagesize = 250;
$offset = 0;
$spacepos = strpos($body," ",$pagesize)-1;
and then use substr to subset that data:
$body = substr($body, $offset, $spacepos);
You can add a link to set $section, which you use to decide where to start you offset
$offset = ($section * $pagesize);
Or you could include tags in your content at positions where you would like split the text, and use those as delimiters