I have the same issue on v2.3.7 for Mac, but I found a workaround. I chose to let the BrewSmith2 application prepare a "print PDF preview" for a larger paper size than I really have, and before actually printing I set the printer's paper size down to regular size again.
1. Go to printing preferences for your printer and set A3 as default paper size. Close the preferences window.
2. Open BrewSmith2 to print recipe, on the print window you should now see the proper text size relative to the paper.
3. Select "PDF | Open PDF in Preview " in the lower left corner of the print page. And keep the Preview application open.
4. Go back to printing preferences for your printer and set A4 as default paper size. Close the preferences window.
5. Switch back to the PDF Preview application in step 3, and print from there. Fingers crossed, you should get a useful printout....
Tip: First time I tried it I had not closed the preferences window in step 4, thus the printing in step 5 still believed I had an A3 capable printer, and the printout was just an enlarged section of the recipe.
Hopefully this will all be fixed properly before long
Cheers,
Karl