>...going to a PDF “printer” or a physical printer (happens to be an old Okidata sprocket-fed impact printer).

>- When going to PDF the data from the @SAYS print, but the “field” being printed has its background printed as grey… basically the footprint of the field is shown, for the actual width of the field rather than the width of the data. This is even if the field printed is empty (i.e., you see a grey rectangle where the field would print).
>
>- When going to print output, the printer prints the data, but ALL spaces—including embedded spaces—appears as two vertical dots (almost like “:”s), again for the entire width of the field being printed. So “Mary Jones” will print like “Mary:Jones:::::::::::::::::::::”.

It sounds like a printer setting, something like "show whitespaces."

What happens if your @ SAY line changes to this:

@ y,x SAY CHRTRAN(whatever, SPACE(1), "_")

Does it print underscores? And can you change it to a different whitespace character to print?

@ y,x SAY CHRTRAN(whatever, SPACE(1), CHR(0))
@ y,x SAY CHRTRAN(whatever, SPACE(1), CHR(255))

Sometimes CHR(255) shows up as a y with two dots above it.