When a company wants to issue a letter to another business, or to a customer or individual, they tend to simply type out a document that will include the reason for their letter. The letter could be a simple call out of a promotional piece that the company wants to inform the ones they are targeting, or they could be writing out a letter that is addressing something concerning about a situation.
In any event, the consistent thing that happens here is the letter is generally written on a piece of stationary that will contain a letterhead at the top of the page and contact information at the bottom of the page. The letterhead tends to have the company logo in it with any branded slogan that goes along with the logo. The colour of the letterhead is typically the same as the company logo as well.
Producing letterheads on a stationary is something that can be done by a graphic designer or a printing company. If you decide to go with a graphic designer to produce the letterhead, that is fine, however, be sure that they understand that you need to be consistent with your corporate identity, i.e. logo has to be the same including colour and branding slogan, nothing can be compromised along the way.
The advantage of choosing a company that can design and print the letterheads for you is you have gone to someone that can consolidate the work for you in one place. If you go to a graphic designer only, you will then need to have your letterheads printed off somewhere.
Well that place can be a Toronto Printing shop that can add value to what it is that you are looking for. They will be abble to create the letterhead for you and then produce that graphic onto a hard copy so you as a company can use it for whatever you need the letterhead for.