As I understand it nothing has changed with regard to the general place of supply rules for services - for B2B supplies where the customer belongs outside the UK you don’t charge VAT (and the customer would have to reverse charge on their end), for B2C supplies of services that don’t fall under the rules for “digital services supplied electronically” you charge UK VAT as the place of supply is the UK.
For B2C supplies that do count as electronically supplied digital services you should previously have been using the VAT MOSS system to charge each customer VAT at the local rate for their country. This is the case where the rules have now changed, since you can no longer use the EU VAT MOSS system from the UK. You now need to either register for non Union MOSS in an EU state, or register for VAT in every separate state where you have B2C customers.
So the question is whether your B2C supplies of PDFs count as “electronically supplied” - is it an automatic process or is there manual intervention required such as you manually emailing the PDFs to the customer?