Definition of folio

Magazines: magazine for people in the magazine industry, published monthly by Hansen Publishing. It covers all aspects of magazine publishing from editorial to fulfillment. Folio also sponsors several conferences and seminars each year.
Printing:

1. page numbers of a book or catalog, often placed at the outside top of a page. Right-handed pages are usually odd-numbered; lefthanded pages are even-numbered. A drop folio is a page number printed at the bottom of a page.
2. brochure, magazine, or catalog comprised of signature and consisting of four pages printed onto one sheet of paper that is folded once, forming two leaves with four surfaces or pages.
3. sheet of 17" × 22" paper.
4. (colloquial) book with exceptionally large pages.