You want the event to be committed in the same transaction as the operation on your database.
In this particular scenario, you can push the event on a queue, which enlists in your transaction, so that the event will never go out unless the aggregate is persisted. This will make creating the PDF eventual consistent; if creating the PDF fails, you can fix the problem, and have it automatically retried.
Maybe you can get more inspiration in one of my previous posts on eventual consistent domain events with RavenDB and IronMQ.