When creating business letters, use 8 ½" by 11" unlined paper. Although 24-pound paper with 100+ brightness is a little more expensive, it will make a better impression than everyday copy paper. Use 1" margins on all four sides. Use a serif font such as Times Roman (12 point) or Georgia (11 point). A business letter should be single-spaced and, if possible, typed on a computer. Print the letter on only one side of the paper. Fold the letter horizontally into thirds. Mail the letter in a No. 10 security envelope (4 1/8" by 9 ½").