src/Module.php
public function renderFile(FileEvent $e)
    {
        $file = $e->getLastFileObject();
        // assume it is of the class Core\Entity\FileEntity
        $return = '<div class="col-md-3"><a href="#attachment_' . $file->getId() . '">' . $file->getName() . '</a></div>' . PHP_EOL
                . '<div class="col-md-3">' . $file->getType() . '</div>'
                . '<div class="col-md-3">' . $file->prettySize . '</div>';
        /*
         * this snippet was for direct inserting an image into the PDF
        if ($file && $file instanceOf FileEntity && 0 === strpos($file->getType(), 'image')) {
            //$content = $file->getContent();
            //$url = 'data:image/' . $file->getType() . ';base64,' . base64_encode ($content);
            //$html = '<img src="' . $url . '" >';
            $html = '<a href="#1">' . $file->getName() . '</a>';
            $e->stopPropagation();
            return $html;
        }
         */
        return $return;
    }
public function renderFile(FileEvent $e)
    {
        $file = $e->getLastFileObject();
        // assume it is of the class Core\Entity\FileEntity
        $return = '<div class="col-md-3"><a href="#attachment_' . $file->getId() . '">' . $file->getName() . '</a></div>' . PHP_EOL
                . '<div class="col-md-3">' . $file->getType() . '</div>'
                . '<div class="col-md-3">' . $file->prettySize . '</div>';
        /*
         * this snippet was for direct inserting an image into the PDF
        if ($file && $file instanceOf FileEntity && 0 === strpos($file->getType(), 'image')) {
            //$content = $file->getContent();
            //$url = 'data:image/' . $file->getType() . ';base64,' . base64_encode ($content);
            //$html = '<img src="' . $url . '" >';
            $html = '<a href="#1">' . $file->getName() . '</a>';
            $e->stopPropagation();
            return $html;
        }
         */
        return $return;
    }
here the inserted File is rendered,
there is a lot which still can be done like outsorcing the HTML to a template,
or distinguish between different File Types,
at the moment we assume the $file is always an (sub-)instance of \Core\File\Entity

@param \Core\View\Helper\InsertFile\FileEvent $e
@return string