This is truly the stuff of nightmares, and I'm definitely going to review our CI/CD infrastructure with this in mind. I'm eagerly awaiting learning what the initial attack vector was.
I heard a story from years ago that security researchers tried leaving USB thumb drives in various bank branches to see what would happen. They put autorun scripts on the drives so they would phone home when plugged in. Some 60% of them were plugged in (mostly into bank computers).
I'm not sure when you started using PDFs (I remember mid-90s when my Dad told me about this cool new document format that would standardize formats across platforms, screen and paper!), but hardly anything is static any more.