What should I do concerning my work as a production manager in a printing press that prints posters for a company that sells alcoholic beverages? Should I leave this job, given that it is my sole source of income?

It is not permissible to work in printing anything related to alcoholic beverages or their promotion, or the promotion of other prohibited things. If your work requires printing these posters, it is not permissible, as it constitutes cooperation in sin and aggression. However, if necessity compels you to remain in this job due to the absence of an alternative that provides the necessities of life for you and those you support, then it is permissible to stay in it until you find another job.