Both your printed projects and your promotional items, while often distributed separately, are they are meant to work together or show off one united marketing campaign.
Your company standards and design styles play a big part in this, but more than that you need to provide both printed and promotional items to your clients as a single marketing plan.
Here is an example. When you meet a potential client, hand out your business card and receive theirs in return. Your business card is a representation of your company, brand and credibility. After you have established contact with your clients then send out or drop off a promotional item that once again represents your brand and plays off the same design of your business card.
After you have supplied them with a promotional item, invite them to join into you cross media marketing campaign that will keep them up to date on your services and will also continue the conversation.
In this case you are using both print and promotional items as well as your more modern marketing strategies to create a relationship with your clients.
Furthermore, with your printed projects and promotions working together, you are going to create better brand awareness and you will notice the difference in your bottom line.