Without Logging restrict a webroot folder to access

I am newer in cakephp .I have a pdf folder under cakephp 3.0 weroot folder parallel to the css and js folder . I have a logging function with cakephp auth component. I want to restrict that pdf folder if user not logged in. Right now if we put the url that pdf file is access either user lodded in or not .

If requested file exists in webroot/, it is delivered directly by server without PHP/CakePHP handling.

Move files out of webroot/ (ex. to files/).

Then send file in your controller

public function getPdf($id)
    // additional auth checks

    $file = $this->Attachments->getFile($id);
    $response = $this->response->withFile($file['path']);
    return $response;