PHP Fatal error: Declaration of Zend_Pdf_FileParserDataSource_File::__construct() must be compatible with Zend_Pdf_FileParserDataSource::__construct() in /lib/Zend/Pdf/FileParserDataSource/File.php on line 41
If you are using Magento 1.8 or earlier with Php 5.4, please make sure that you apply the patch for PHP 5.4 support as supplied to Magento - see here for details.
It includes a few changes in the Zend pdf code which would otherwise error out on 5.4.