How to use external css in tcpdf pdf generation

To include external CSS file, you can do as below before you add your HTML content

$html .= '<style>'.file_get_contents(_BASE_PATH.'stylesheet.css').'</style>';

By this, while you pass $html to generate pdf it will include those styles.

As far I am aware, there is no need for including Javascript into a PDF. The purpose of a PDF is to display a non-interactive static content, which can be achieved by HTML and CSS