Once you have things set up for one Document Type, one file format, one business partner, decide where to expand next.
The safest thing to do is attach that same EDI Profile to other business partners first. This lets you test what you've done already to make sure it really is general and will work well.
Then add a second Document Type to that same EDI Profile, configure it with the same caution, and then expand usage to more business partners.
Over time you may learn that all you need is one EDI Profile with a couple of EDI Forms, all attached to all of your Customers.
As the business environment changes and your partners start to change their businesses, you may find that you need to build new EDI Profiles for particular partners. This is fine. As long as you started slowly and started generally, you should find that the number of EDI Profiles will stay relatively small and easy to manage.