In response to feature requests, we have built in support for generating PDFs directly from HTML (and you can use PHP or VaeML code too!).
Rather than fiddling with complicated software packages or PHP libraries, just design your PDF documents the same way you would design a webpage: with HTML and CSS. Almost all HTML and CSS is supported (the main exception being nested tables).
We use the dompdf library to handle PDF generation. Any file ending in .pdf.html will automatically be run through the PDF engine. Any file ending in .pdf.haml will be run through Haml and the PDF engine. Files ending in .pdf.php, or .pdf.haml.php will also be run through PHP.