Automatically Add Existing PDF File to New PDF

We have an existing PDF file containing our Purchase Order (PO) Terms & Conditions (Ts&Cs) and would like to add this file every time we print a new PO to PDF.  For example, a new 2 page PO is printed to PDF, and we would like the 3 page Ts&Cs automatically added, resulting in a 5 page (2+3) properly sequenced document.