One Serial Number creates a single, unique Product ID. If I have more than one product, do I need more than one Product ID?
Generally, yes. If you had only one Product ID then if more than one product was installed on a single machine each product would have to share the same Licence Policy.
How many Licence Keys can I distribute for my product and do I have to pay a royalty?
Once you have purchased a Serial Number for your product you can issue an unlimited number of Licence Keys without any further payment.
Upon purchase of the full product is there any additional documentation, examples etc. or is everything provided with the evaluation kit?
Everything is included in the evaluation kit.