Postage is determined by weight. A Forever stamp will be enough to cover a regular envelope that weighs less than 1 ounce. If you have 2-3 pages in a regular letter size envelope, a Forever stamp will probably be fine. If you have many pages, or use a large flat envelope, then you should go to the post office teller and have them weigh the envelope to determine the postage. When in doubt, have it weighed.
