Hi VELV,
Thanks for bringing your question to the forum. Local SEO is largely based on the physical location of the business, not its menu of services. As you describe it, you have a single company at a single location, with a varied menu of services. This might be comparable to an HVAC company which both installs air conditioners and repairs hot water heaters. It's a single company, doing multiple things. The HVAC company, and your business model of a single business with a varied menu, at a single location, is eligible for just one Google My Business listing, and if you choose to move ahead with the model you've described, your business will be "optimizable" in all the various ways one would typically market a single local business.
The alternative to this would be to legally register your single companies as two distinct businesses, with unique tax IDs, unique phone numbers, business names, and completely distinct Google My Business categories. Envisioning your printing company as completely separate from your website design company is an option, but it has potential problems.
The first problem would be that co-located businesses can sometimes be filtered out of Google's high level mapped search results, particularly if they are in a shared category. This is why I'm emphasizing that you would need no crossover between categories. Even with distinct categories, there is some chance you might experience some filtering. More concerning, though, would be the possibility that Google might decide that your two businesses are actually one business attempting to appear like two, in which case they might suppress or remove one of your listings. Your best defense against that would be going to all the necessary lengths to legally register the second business, and keeping its phone number, website URL, and other assets separate, and not linking between the two businesses in any way.
It's a choice you need to make about how you want to envision and present your enterprise. The easiest route will be as a single business with a menu of services. You can select categories for both services on the GMB listing, and build out great content for both on your website. But if you want to move ahead as the owner of two separate businesses, you'll be best served by taking the necessary steps to register and run the two brands, perhaps with the eventual goal of a separate physical location for each business. In that case, the concern about co-location and filtering goes away!
Hope this helps, and please let me know if you have any further questions. Good luck to you!