Use an online event ticketing platform for visitors to register. It cuts back on paper use and organises your registration list for easy reference. It is generally simple to setup and you can have your event site up and running in no time. Many of these event ticketing platforms integrate seamlessly with social media platforms like Mailchimp, Facebook and Twitter which makes it easier to use your existing mailing list or target a wider audience. They are also mobile friendly and work well across-platform e.g. Android & iPhone.
Cons are primarily in the form of fees for use. However, the advantages usually outweigh the cons by far.