Fatal error: Uncaught Error: Call to undefined function add_action() in /users/laufgruppe-lvb/www/wordpress/wp-content/plugins/_pdf-viewer-for-wordpress/includes/tinymce/button.php:14 Stack trace: #0 {main} thrown in /users/laufgruppe-lvb/www/wordpress/wp-content/plugins/_pdf-viewer-for-wordpress/includes/tinymce/button.php on line 14