Here is a note i feel important for newbies
$url = PDF_create_action($p, "URI", "url=http://www.pdflib.com");
PDF_create_annotation ($p, 44, 100, 55,700, "Link", "linewidth=0 action {activate $url}");
Above 2 lines will change the hand
cursor once your cursor is in the rectangle as assigned by the
create_annotation command. Once you click in that area, it will
bring you to the url in create_action command.