Once Upon a Secretary (1983)

Nina is a porn star. Sharon is a secretary who wants more than just sex from her married boss Mr. Murphy. Meanwhile, tired Nina falls asleep before sex with her boyfriend Brad. He therefore calls in their neighbor Elaine as substitute. Nina wakes up but just joins in until falling asleep again. Pressured for a less tiresome job, Nina applies for a strip bar, but gets too comfortable with the clients. Meanwhile, Mr. Murphy rewards Sharon after asking her to pleasure two businessmen. Realizing she's getting paid for sex, Sharon accepts her coworker Steve's offer to become a porn star. Steve introduces Sharon to Nina who shows Sharon the ropes. They decide trading jobs. Brad comes working for Mr. Murphy too, to protect Nina from the boss who has to overhear the couple's own office sex. Sharon convinces Steve to get on camera with her.