@majonathany On the product page, you can add them to the liquid template file of your product page like so to protect against any future asset_url change:
View Certificates of Analysis
You would however want to be very careful about your QR code and use a QR service that embeds a static URL that points dynamically to a URL you specify as otherwise the QR code could not be changed in the future.
You’d want to protect against instances where the certificate URL was forced to change for any reason.
Personally - given the importance of these certificates to your business - I would set up a subdomain like https://certificates.example.com/file-name.pdf to ensure that I had full control of certificate names on my end without reliance on anyone else’s software. You could then generate QR codes without the need for ongoing costs and swap out certificates (or redirect urls) as needed.