Change pdf format from portrait to landscape

Edit 

app/code/community/Fooman/PdfCustomiser/Model/Invoice.php

change the letter P in the code below to L

if (empty($pdf)) {
    $pdf = Mage::getModel(
        'pdfcustomiser/mypdf', array(
            'P', 'mm', Mage::getStoreConfig('sales_pdf/all/allpagesize', $storeId), true, 'UTF-8', false, false
        )
    );
}