Her diary, written during her time in hiding, is one of the most moving testimonies of the war, and more than 30 million copies have been sold.
"These - literally - uncovered texts bring the inquisitive and in many respects precocious teenager back into the foreground".
They photographed the pages, backlit by a flash, and then used image-processing software to decipher the words, which were jumbled with the writing on the other side of the pages.
The hidden pages were covered up with brown gummed paper, but new technology has allowed researchers to reveal four "dirty" jokes and 33 lines about sex education and prostitution, adjacent to five, crossed out phrases according to the Anne Frank House.More news: Golden State Warriors beat Rockets on the road 119-106
The story is set in 1942 when a 13-year-old Jewish girl and her family fled their Amsterdam home and went into hiding following the Nazis' occupation of Holland.
Frank Van Vree, director of the Netherlands Institute for War, Holocaust and Genocide Studies, said the jokes are of the sort that are "classics among growing children".
Announcing their discovery on Tuesday, the Anne Frank Foundation believes the text helped the teenager express her sexuality.
The pages, dated to September 28, 1942, were contained in the red-and-white checkered diary Anne had received for her birthday in June of that year, shortly before they went into hiding. "She also writes about it on other, uncovered pages", said Ronald Leopold, executive director of the Anne Frank House. "They make it clear that Anne, with all her gifts, was above all also an ordinary girl".More news: It's back to work for Sonam Kapoor post her starry wedding
In a snippet of the text, she explains how women get their periods around 14 years of age, and said it "a sign that she is ripe to have relations with a man but one doesn't do that of course before one is married".
On prostitution, she wrote: "All men, if they are normal, go with women, women like that accost them on the street and then they go together". On prostitution, Frank noted that "in Paris they have big houses for that".
"The diary of Anne Frank is a world heritage object with great historical value, and this justifies research into it", the institution said.
Otto Frank, the only family member to survive the Holocaust, returned to Amsterdam after the war.More news: US Treasury, UAE sanction Iran money exchange network
Anne died in the Bergen-Belsen concentration camp three months before her 16th birthday, in 1945.