How to add PDF file into blockcert json file

Our students are getting course certificates on pdf format. How to make that pdf to be used to issue certificates in Blockcert v2

@sophie I missed that sorry. In Blockcerts v3 this will be possible by embedding the base64 encoding of the pdf into the blockcerts.
Blockcerts v3 beta is already available (and supports that) for issuance and verification.