In order for Catalog PDF module to be compatible with the Quotation module, you need to modify the following configuration file: /modules/quotation/quotation.php
At the top of the file (line 13), you need to REPLACE:
include_once(dirname(__FILE__).'/tools/includes.inc.php');
include_once(dirname(__FILE__).'/models/includes.inc.php');
BY:
if( (empty($_GET["controller"]) || $_GET["controller"]!="AdminSCPDFCatalog") && strpos($_SERVER["REQUEST_URI"], "/scpdfcatalog/")===false)
{
include_once(dirname(__FILE__).'/tools/includes.inc.php');
include_once(dirname(__FILE__).'/models/includes.inc.php');
}