Yes, you can select different permissions for each of your customers if you wish.
Simply scroll down to the bottom of your Customer Portal page to see a list of all your customer portal users.
Select one of your portal users. Here you are able to add extra templates as well as tweak their permissions.
Click on "Customize Permissions" to set different permissions for your Customer Portal User
Make the changes required and click "Update Portal User"
If you need to, you can also give a customer portal user permission to work with multiple customers. This can be useful if you have a third party who needs the ability to create jobs for a number of different customers.