A brochure (derived from a French word meaning "to stitch") is a paper-covered booklet, usually not longer than 24 pages. A leaflet is a small flat or folded sheet of printed matter, usually not exceeding 4 pages in length. A pamphlet is a complete unbound publication of less than 100 pages, stitched or stapled together. These terms are often used interchangeably, understandably so, since neither the printing trades nor dictionary makers have agreed on their precise meanings. If the printed item is quite small, call it a leaflet; if larger, a brochure; if almost the length of a small book, a pamphlet.
Dictionary of problem words and expressions. Harry Shaw. 1975.