Hi Neil, I have come to the conclusion that the modern web browser does an excellent job at converting HTML to PDF.
Have a look at https://hollandtrade.com.au/wcart/, add a product or two, change the quantities and print or create a PDF.
All it takes is an inclusion of a button (or similar) like:
<button class="btn" onclick="javascript:window.print();"><i class="fas fa-print"></i> Print the Invoice</button>