Hi AstonAtom ,
I understand that you're talking about the PDF generated by PO Pro. Am I right?
If so, you can customize the PDF by overriding any of the templates you can find in 'atum-purchase-orders/views/pdf-templates'.
You can also create new templates using the 'atum/purchase_orders_pro/po_pdf_templates' filter.
Best Regards,
José Andrés