Thanks for taking the time to answer.
The file I'm thinking of at the moment is actually a payment summary, so it's not the same as the receipt created by the debit machine. I would like to share it with the individual students somewhere they can access repeatedly. In the past we have emailed these documents out but when students need them in the future they often can't find the original email and contact us again and it's a big hassle.
How would you suggest we set up the Assignment module to do this? Can we create an assignment that's completely unlinked from the gradebook? And can we post a feedback document without the student having to take any action first?