It occasionally happens that pages in a newly-purchased book are attached to one another at the edges, and one needs to run his hands in between the two pages to separate them. Is this permissible on Shabbat, or does this violate the prohibition of "Kore’a" – tearing on Shabbat?
The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1839-1933) addresses this question in Parashat Ki-Tisa (12), and he rules that separating the attached pages is permissible on Shabbat. He explains that the prohibition of "Kore’a" applies only to separated attached items that were intended to be permanently attached, which is clearly not the case with pages of a book that are stuck together. What’s more, the factor did not even intend for the pages to be stuck together, and this occurred accidentally. Therefore, separating the pages does not fall under the prohibition of "Kore’a."
Summary: If two pages of a book are stuck together, it is permissible to separate them on Shabbat.