This is BIG >> "I have contacted the doctor to verify he is indeed invited to write a paper in that Journal. The doctor replied to me and send me the paper draft. However, because the paper is not published yet, I can't post it here for everybody's review. This is the protocol in the academic world. After the paper is published in the Journal, everybody will be able to see it.
The good thing is that the doctor has agreed to publish his poster in the conference, probably on his website. The main content in his conference poster, the draft, and the paper to be published in the Journal are the same.