increased version, deletes old config data

app/code/community/FireGento/Pdf/etc/config.xml

@@ -2,7 +2,7 @@
 <config>
     <modules>
         <FireGento_Pdf>
-            <version>1.0.0</version>
+            <version>1.1.0</version>
         </FireGento_Pdf>
     </modules>
     <global>
@@ -33,6 +33,13 @@
                 </rewrite>
             </tax>
         </models>
+        <resources>
+            <firegento_pdf_setup>
+                <setup>
+                    <module>FireGento_Pdf</module>
+                </setup>
+            </firegento_pdf_setup>
+        </resources>
         <events>
             <firegento_pdf_invoice_insert_note>
                 <observers>

app/code/community/FireGento/Pdf/sql/firegento_pdf_setup/upgrade-1.0.0-1.1.0.php

@@ -0,0 +1,44 @@
+<?php
+/**
+ * This file is part of the FIREGENTO project.
+ *
+ * FireGento_GermanSetup is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * This script 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 General Public License for more details.
+ *
+ * PHP version 5
+ *
+ * @category  FireGento
+ * @package   FireGento_Pdf
+ * @author    FireGento Team <[email protected]>
+ * @copyright 2013 FireGento Team (http://www.firegento.de). All rights served.
+ * @license   http://opensource.org/licenses/gpl-3.0 GNU General Public License, version 3 (GPLv3)
+ * @version   $Id:$
+ * @since     0.1.0
+ */
+/**
+ * Invoice model rewrite.
+ *
+ * The invoice model serves as a proxy to the actual PDF engine as set via
+ * backend configuration.
+ *
+ * @category  FireGento
+ * @package   FireGento_Pdf
+ * @author    FireGento Team <[email protected]>
+ * @copyright 2013 FireGento Team (http://www.firegento.de). All rights served.
+ * @license   http://opensource.org/licenses/gpl-3.0 GNU General Public License, version 3 (GPLv3)
+ * @version   $Id:$
+ * @since     0.1.0
+ */
+
+/* @var $this Mage_Eav_Model_Entity_Setup */
+$installer = $this;
+$installer->startSetup();
+
+$installer->deleteConfigData('sales_pdf/firegento_pdf/engine');
+
+$installer->endSetup();