Thanks for the suggestion. I have tried Brave and Firefox. Both allow the invoices to be printed, but both have the problem of the old Safari offering:

the font size being too small, 

the money amounts not visible in portrate mode

even in landscape mode, the font size  is about 8pt, or at the most 10pt, which is too small for comfort.

huge amount of wasted space which could be used for a larger font.

Is there a way of increasing the font size? 

Printer is a Canon MB5100