"He is a professional actor."
Translation:On jest zawodowym aktorem.
That would sound weird, "aktor zawodowy" is not a separate profession, "zawodowy" simply describes it and therefore should be at the front.
Compare with "aktor teatralny" (theatre actor), which sounds a lot better in such a word order because it is kind of a set phrase.
I think we have "He is an actor by profession" somewhere else and that would be "On jest aktorem z zawodu".