@fanfare
New York requires PDF attachments to the state tax return in certain cases. The TurboTax New York program allows PDF attachments to an e-filed New York return only in the CD/Download software, not in TurboTax Online. It's possible that some other states have the same capability.
TurboTax Business (not Home & Business) also allows PDF attachments to e-filed returns, but you can't file a Form 1040 personal tax return with TurboTax Business.
As far as I know, those are the only situations where you can attach a PDF to an e-file in TurboTax. The posts that you see about attaching a PDF may be referring to these situations. I'm certain that you cannot attach a PDF of a Form 8949 or brokerage statement to a federal Form 1040 e-file in TurboTax.
