Read MoreBill Ackman's 'hugely important' move
While the tools like websites and phone systems to help sell are optional, the former distributors described the pressure they felt to purchase the products in order to improve their chances of business success. They also noted the emphasis on signing up new distributors over actually selling the nutritional shakes that are the company's signature product.
"To this day I feel terrible about the people I brought in," said Darilyn Listort, a retiree from Boynton Beach, Florida, about the people she recruited. "It doesn't work."
Herbalife issued a strong rebuke to the Pershing Square-funded film.
Read MoreElite investors: Herbalife is legit
"Herbalife views the release of this advertisement posing as a 'documentary' as nothing more than propaganda," the company said in a statement. "The company believes this is yet another tactic in Mr. Ackman's calculated, coordinated and well-funded effort to destroy a 34-year-old company and support his $1 billion bet against Herbalife,"
Herbalife also criticized the event's moderator, multilevel marketing expert Robert FitzPatrick.
"He is a known critic of the industry, and a consultant to Mr. Ackman and three-time convicted felon and perpetrator of fraud Barry Minkow," the statement said. "Herbalife believes Mr. FitzPatrick's involvement is further evidence that this 'documentary' is merely another biased attack on our company."
Read MoreHerbalife beats expectations, suspends dividend
Ackman said in remarks that the idea behind the film was to highlight middle-class people duped by Herbalife. Much of the previous focus has been on low-income Hispanics involved with the company through so-called buying clubs.
The hedge fund manager said the participants in the documentary had not been paid, but that Pershing Square had covered their travel expenses to New York City for the event. He said he did not meet the participants before the Friday premier.
—By CNBC's Lawrence Delevingne.