protected function _buildPermissionsArgument()
    {
        $permissions = $this->_Pdf->permissions();

        if ($permissions === false) {
            return false;
        }

        $allowed = [];

        if ($permissions === true) {
            $allowed[] = 'AllFeatures';
        }

        if (is_array($permissions)) {
            foreach ($permissions as $permission) {
                $allowed[] = $this->_permissionsMap[$permission];
            }
        }

        return implode(' ', $allowed);
    }