Never assume your current clients know all you can do for them. The best way to get more business is to get more from existing customers. The only way you can do that is to keep telling them all that you do. One marketing strategy for this is to send out a printed piece that lists all the things you do followed by pieces that expand on each individual item. The way a printer might do this is to create a piece that talks about brochures, business cards, wide format printing, book binding, and so forth, with a short paragraph about each thing. This would then be followed with a postcard that talks more about each individual item.
This strategy works well for most businesses -- from lawn care to lawyers. Mowing, landscaping, xeriscaping, etc., followed by details of what each of those things is and why. Litigation, taxes, wills, etc., you get the picture.
Keep telling people about the things you do, and don't get frustrated if they don't seem to "get it" right away. No matter how many years I've been working with a printing client, I still get people walking in who say, "Oh, you do that? I had no idea!" It can be frustrating when you think you've gotten your message out...but that sentence is an opportunity for me to tell people about all my printing and marketing services...and it is an opportunity for you to tell people what you do, too.