The process should be exactly the same.
You will need to make sure your customer portal account has your license number as a registered product (via 'Register My Products') so that they can find you as a supported customer.
(apologies if I now tell you something you already know)
Click 'API Support' under 'My Support' in your customer portal account
Click the link 'Document Manager Key Request'
Click the link 'Request New Document Manager Key'
Fill in the form
Sit back and wait it can take a couple of days