Sorry you can only transfer from 2017 at the beginning before you start. You would have to start over in a new return, go up to File-New.
Or you will have to manually enter anything you need from 2017. But a pdf won't help you anyway. It only transfers basic info like your name and ssn. And you can only transfer Pdf from a few programs. https://ttlc.intuit.com/questions/4120237-can-i-transfer-last-year-s-pdf-into-the-2018-turbotax-for-...
