“It’s a very cautious start to her becoming a writer,” he said. “It’s still very early stages.”

The two newly revealed pages were written in Frank’s first diary, with a red plaid cover, on Sept. 28, 1942, when she was 13 years old. During her time in hiding, she wrote two versions of the diary. The first was written in a series of small notebooks, from her 13th birthday on June 12, 1942, until Aug. 1, 1944, and was intended strictly for herself.

But one day she heard on the radio that the Dutch government in exile was planning to publish eyewitness accounts of people’s suffering under the German occupation, and she resolved to write a new book that she called “The Secret Annex,” based on her diaries, which she hoped to submit after the war. She completed 215 loose pages in a couple of months, but in August 1944, she and her family were discovered, arrested and deported; she died in the Bergen-Belsen concentration camp three months shy of her 16th birthday, in 1945.

Mr. de Bruijn said Frank may have also pasted over the pages as a form of self-editing as she revised her diary in preparation for the second, public version.

Researchers at the Anne Frank House discovered the two hidden pages in the original version of the diary while they were checking its condition and photographing the pages in 2016. The notebooks are in storage for safekeeping and only examined once every 10 years.

Until now, the technology that would have allowed researchers to look at the covered pages without destroying them wasn’t available. “When you touch the pages they can be damaged, so we don’t touch them,” said Teresien da Silva, head of collections at the Anne Frank House. Using photo-imaging software, they were able to decipher text beneath the brown paper without any contact with the pages.

Could it be considered disrespectful to reveal pages that Frank wanted to hide?