Export all Magento Invoices as PDF

export.php

<?php
// this file should be copied to root
require_once('app/Mage.php');
Mage::app();
$maxOrderId = 24346;

for($orderId = 1; $orderId < $maxOrderId; $orderId++) {
  $orderObject = Mage::getModel('sales/order')->load($orderId);
  echo "$orderId of $maxOrderId\n";
  $invoiceCollection = $orderObject->getInvoiceCollection();

  try {
    $pdf = Mage::getModel('sales/order_pdf_invoice')->getPdf($invoiceCollection);
    $time = new DateTime($orderObject->updated_at);
    $id = $orderObject->getIncrementId();
    $name = 'i_'.$orderId.'_'.$id.'_'.$time->format('Y-m-d_H-i-s'). '.pdf';
    
    mkdir(Mage::getBaseDir('var'). DS . 'tmp' . DS.  $time->format('Y'), 0777);
    mkdir(Mage::getBaseDir('var'). DS . 'tmp' . DS.  $time->format('Y')  . DS . $time->format('m'), 0777);
    
  $pdf->save(Mage::getBaseDir('var'). DS . 'tmp' . DS.  $time->format('Y') . DS . $time->format('m') . DS. $name);
  } catch (Exception $e) {
    echo 'Not possible:',  $e->getMessage(), "\n";
  } 
  
}