This is a fairly easy system. I don't know how it is done exactly here at phpbuilder, but you just need a table wich holds two columns: the id of the page and the comment to be displayed (off course, you can add extra information like mailaddress etc). Select the records with the id you want from the table (simple sql) and loop through the results, presenting the comments.
Adding a comment is also just inserting a form with 1 field (the id is in YOUR code) for the comment...
