When I try to print the partnership IL-1065 to mail, the 'sign here' section says "Self-Prepared" where my signature should go?! (Turbotax Business 2018)

Yes! Same thing happening to me.

"'sign here' section says "Self-Prepared" where my signature should go"

You sign above that section (see screenshot).

I know where it should be signed. Turbotax generated my PDF with a large 'Self-Prepared' stamped OVER the signature box. I can't attach an image?