Oscommer - pdf invoice attachment

We use Oscommerce 2.2. What I want is an add on module for the customer to view the pdf invoice per order, specifications as follow: 1. All pdf invoices will be load up onto the same directory folder (these are final invoices generated by our MYOB retaill software). 2. pdf invoice name is order number .pfd e.g [login to view URL] for order 156067. 3. When the customer log onto the his/her account and view his order, a button to indicate "View pdf invoice" 4. Admin can attach the pdf file to server with a click of the button. 5. The user can not view other invoices not belong to them and the directory folder is hidden, user can not find by viewing the source. 6. I have a supplier website has this function, they use something call filepush, it really good. Let me know if you have any question.