Why create one? _ "Re_inventing the wheel", is no fun. If you work for a single organisation it's likely that your templates could last a long, long time with no need to go back to the design board every time you are asked to create a new manual or user guide. When you work for yourself it's a great way to show clients that you have the skills they are looking for without breaking any confidentiality clauses with your existing clients, and with just a little bit of luck they'll adopt your method of working so you can continue to recycle your past efforts too.
Creating Envelopes _ Your letter will not be complete unless you have an envelope also formatted appropriately. What's good about this function is that you can either customize your own envelope or allow Word to come up with a matching envelope to the letter you have written using the application. What it does is it automatically copies the address and uses it to create the envelope. That helps you do away with manual typing.