In my opinion, the ability to attach files to PDF ranks very high in the (long) list of PDF features that have a lot of power but are not widely used. Standards define ways to embed additional machine readable information into a PDF overcoming the dilemma that has been reported as "PDF is where data dies".
Nothing is better than facetime with customers when explaining something that might be complex and needs a simple push to get going. The content is mostly propelled by feedback from our customers, as well as questions fielded by our Customer Support team (both at callas and Four Pees) giving everyone a chance to learn something new.