Last summer, as the release of “It Ends With Us” approached, Justin Baldoni, the director and a star of the film, and Jamey Heath, the lead producer, hired a crisis public relations expert.

During shooting, Blake Lively, the co-star, had complained that the men had repeatedly violated physical boundaries and made sexual and other inappropriate comments to her. Their studio, Wayfarer, agreed to provide a full-time intimacy coordinator, bring in an outside producer and put other safeguards on set. In a side letter to Ms. Lively’s contract, signed by Mr. Heath, the studio also agreed not to retaliate against the actress.

But by August, the two men, who had positioned themselves as feminist allies in the #MeToo era, expressed fears that her allegations would become public and taint them, according to a legal complaint that she filed Friday. It claims that their P.R. effort had an explicit goal: to harm Ms. Lively’s reputation instead.

Her filing includes excerpts from thousands of pages of text messages and emails that she obtained through a subpoena. These and other documents were reviewed by The New York Times.

There have long been figures behind the scenes shaping public opinion about celebrities — through gossip columns, tabloids and strategic interviews. The documents show an additional playbook for waging a largely undetectable smear campaign in the digital era. While the film, about domestic violence, was a box office hit — making nearly $350 million worldwide — online criticism of the actress skyrocketed.

“He wants to feel like she can be buried,” a publicist working with the studio and Mr. Baldoni wrote in an Aug. 2 message to the crisis management expert, Melissa Nathan.