luos/workflow/engine/methods/processes/processes_DownloadFile.php

<?php
/**
 * processes_DownloadFile.php
 *
 * ProcessMaker Open Source Edition
 * Copyright (C) 2004 - 2008 Colosa Inc.23
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 *
 * For more information, contact Colosa Inc, 2566 Le Jeune Rd.,
 * Coral Gables, FL, 33134, USA, or email info@colosa.com.
 */
//add more security, and catch any error or exception


$sFileName = $_GET['p'] . '.pm';
$file = PATH_DOCUMENT . 'output' . PATH_SEP . $sFileName . 'tpm';
$filex = PATH_DOCUMENT . 'output' . PATH_SEP . $sFileName;

if (file_exists( $file )) {
    rename( $file, $filex );
}

$realPath = PATH_DOCUMENT . 'output' . PATH_SEP . $sFileName;
G::streamFile( $realPath, true );