In order for you to bulk export your invoices, simply go to:
WooCommerce > Orders > Bulk Actions
Click on this dropdown menu and the option ‘Bulk Export PDF Invoices’ should be visible. Simply tick the boxes of the invoices you would like to export and click ‘Apply’.
All your invoices will now be saved in a handy little .rar or .zip. If you do not understand what this file is, please have a look at this link and install winrar.