This is a Kohana (3.x) module which providers a wrapper for wkhtmltopdf:
http://code.google.com/p/wkhtmltopdf/

Basic usage to force a file download:
wkhtml::topdf($html_content, 'downloaded_file_name.pdf');

Or to get the PDF file contents:
$pdf_content = wkhtml::topdf($html_content);