Email Notification: Send a pdf via email

I tried

add_filter("gform_user_notification_attachments", "add_attachment", 10, 3);
function add_attachment($attachments, $lead, $form){

    //getting wordpress upload folder
    $upload = wp_upload_dir();
    $upload_path = $upload["basedir"];

    $attachments = array();

    //add a file from the uploads folder
    $attachments[] = $upload_path . "/my_file.jpg";

    return $attachments;
}

and i cant get this to work.