When designing a piece that will be enclosed in an envelope, it's important to consider size and shape of the document, not only for appearance but because if custom-sized envelopes are required it adds to the cost and complexity of the job. A custom envelope size or shape can also add to mailing costs or require use of a separate mailing envelope.
Many printers stock or produce a wide variety of standard envelope sizes. Choose an envelope that fits your piece and fit your piece to a standard envelope.
More ways to Design With Printing in Mind that can save time and money.