Additional Options\Printing
Block printing in this workbook - do not allow the end user to print this workbook. Print and Print Preview operations are blocked. You can modify this behaviour from VBA macro and enable\disable printing in locked workbook. You can find more information in the How to topic.
Users, who can print this workbook - if you've disabled printing in this workbook, you can specify list of Windows users, who can print it. This feature should be used if you know user names of your customers.