Original: In order to count as a pamphlet, UNESCO requires a publication (other than a periodical) to have 'at least 5 but not more than 48 pages exclusive of the cover pages'UNESCO definition; a longer item is a book.
Simplified: In order to count as a pamphlet, UNESCO requires the pamphlet to have 'at least 5 but not more than 48 pages' not including the cover pageUNESCO definition; a longer item is a book.