Is the job of a pharmaceutical sales representative forbidden (haram) or permissible (halal), taking into consideration that the doctor receives compensation (a conference, a leisure trip, or a percentage of sales) for promoting the medicine?

The nature of the doctor's relationship with the work has not been clarified. Does the doctor ask for money to cooperate with you, or does your employer give him money, or do they authorize you to cooperate with him to promote the medicine? In any case, there is no harm in promoting medicine as long as it does not involve deception or fraud. As for cooperating with a doctor for promotion, there is a detailed explanation for that.