I wish to update my Printshop to MacOS 11.2.3. Is this possible

Go to the Printshop website and get the latest version which is noted to be compatible with "11.1 (upward)". There probably will be a fee and it's an upgrade from earlier versions.

Just an FYI that others that have obtained the (allegedly compatible) PrintShop 5 product for macOS Big Sur were unhappy with it compared to their older version 4 prior to Catalina. This is a memory stretch, but I believe one of the plaintiffs in these communities mentioned that it did not honor past PrintShop data formats, so it would be wise to investigate before taking the plunge on the new product.