Yes you can but you must be subsribed to the Enterprise plan to be able to do this.

• This can be done by goin to "Setup", "Owners, Users and Locations" an clicking on 'Manage Users".
• Click on Add, to add a user.
• You will want to add your customer as a Read-Only User so that they can only view information.
• When choosing the Owner, make sure you select the customer in question. Doing this ensures they can only access information regarding them and not anything else.
• Save the form and the user will be created.