Hi Rob. I will try to explain it better.
I need the word "CATS" in black, with no background around it.
This word will be printed on many different surfaces with different patterns (some of them will be transparent, like glass), and these surfaces need to be visible. That is why I need the transparent PDF file with "CATS" word in black color, with NO BACKGROUND around this word.
An example: the print company have a silver paper. And I need them to print the "CATS" word on that silver paper, so the printing machine will not print ANYTHING ELSE: only the word "CATS" will be printed, and original silver surface will be visible around that word. So no other prints except the dlack word "CATS". Just like you would make a black (rubber)stamp on a silver paper, or on any other surface.
Maybe it is because English is not my native language, but I do not actually understand your concern: when you export a PDF from InDesign, there is no background (unless you create one with a colored frame). So, if there is nothing behind the word “cats”, there is no problem.