Solution:
unhooking the paypal module from the displayPDFInvoice hook will also work.
If bank details are required, after unhooking, install the module from this post https://www.prestashop.com/forums/topic/119664-solved-generate-pdf-invoices-bank-wire-payment/?do=findComment&comment=2530505
Works for Prestashop 1.6
Source: https://www.prestashop.com/forums/topic/119664-solved-generate-pdf-invoices-bank-wire-payment/?p=2498597
and
https://www.prestashop.com/forums/topic/560290-upgrade-1617-problem-with-invoice-pdf-template/?p=2541899