Fatal error: Uncaught Error: Interface "PDFEmbedder\Viewer\ViewerInterface" not found in /users/laufgruppe-lvb/www/wordpress/wp-content/plugins/pdf-embedder/src/Viewer/Viewer.php:15 Stack trace: #0 {main} thrown in /users/laufgruppe-lvb/www/wordpress/wp-content/plugins/pdf-embedder/src/Viewer/Viewer.php on line 15