Answer
Use Report PDF Inserts together with a Report Rule: upload the standard PDF (like your Terms and Conditions document) as a Report PDF Insert, then build a Report Rule for the Quotations Report that references that insert and appends it — for example, at the end of the report's own output — every time the report is generated. This combination is what lets a static PDF get automatically bundled with a report's output by default, without needing a manual attach step from the user each time.