Yes, and there are multiple ways to offer free trials:
The preferred method is to add a free period at the beginning of paid SaaS offers (one month) and VM image offers (one or three months). The customer will receive a $0.00 charge, and after the trial period ends, the subscription automatically changes to paid. The contract term then starts at that point.
You can create a SaaS offer listing that takes the customer to a web address of your choice to start a trial outside of the commercial marketplace. Some offer types support a Test Drive that lets you provide the customer with a demo.