In Futurama's first episode "pilot 3000" we are introduced to the idea that individuals were implanted with a career chip that labeled you with "your permanent career assignment" according to Leela.
Ultimately, this would at least suggest (at least to me) that jobs were predetermined. Also, keep in mind that Leela also mentioned that you would shot into the sun if you didn't do your job which does give the suggestion that you are only allowed to do this job and nothing else.
However, later in the series in the episode "Law and Oracle" we discover that you can legitimately move to a different career therefore giving the suggestion that jobs were not predetermined.
My question is: Were jobs predetermined or were they not?