...Using PDFLib improves performance and reduces the memory requirements of dompdf somewhat, while the R&OS CPDF class, though slightly slower, eliminates any dependencies on external PDF libraries.
dompdf - the PHP 5 HTML to PDF converter. dompdf is a (mostly) CSS compliant HTML rendering engine written in PHP. It supports external stylesheets, inline style tags, and the style attributes of individual HTML elements. Requires PHP 5.