Create a custom form that Portal users can be sent to complete

For select ideas, we require additional details re the business justification, impact, KPIs etc. We would like to be able to send a template for the additional information that is linked directly from the idea to the person that submitted the idea. Ideally the document would auto populate with the idea creator name, idea reference # and be date stamped. The Creator would complete the information and the document would be attached back to the idea.