webform_submissions_entity_print_operation.php

/**
 * Implements hook_entity_operation_alter().
 */
function hd_entity_print_uuid_entity_operation_alter(array &$operations, \Drupal\Core\Entity\EntityInterface $entity)
{
  if ($entity->getEntityTypeId() === 'webform_submission') {
    $operations['pdf_download']['title'] = t('Download PDF');
    $route_params = [
      'entity_type' => $entity->getEntityTypeId(),
      'entity_id' => $entity->id(),
      // This should not be hardcoded
      'export_type' => 'pdf',
    ];
    $view_mode = 'html';
    $route_options = ['query' => ['view_mode' => $view_mode]];
    $operations['pdf_download']['url'] = \Drupal\Core\Url::fromRoute('entity_print.view', $route_params, $route_options);
  }
}