9 x 12 Booklet Envelopes are the professional way to send flat but bulky materials- pamphlets, brochures, sales literature, booklets, annual reports, magazines, or catalogs. When you can't, or shouldn't fold the contents, this is your envelope. The envelope's flap is usually rectangular in shape and located on the long edge, booklet, of the envelope. Available in multiple colors, and collections. Order plain or printed.