The summary step supports a print button. To print the summary step, first drag a summary into your workflow from the palette and then setup summary fields to indicate which form fields to display in the printable summary.
Add your own Print Button
It is also possible to add your own print button to any workflow step by adding a Message control with the following html. Note that a custom print button will print the current step and not the entire workflow. Also the current step will print even if the step's print property is unchecked.