you can create 1 pdf for free every 30 days on a rolling basis

"Is this new or has it always been a limitation?"

Yes, it's a known limitation of PDF Maker for Acrobat Reader.

This is a Microsoft command. You should ask in a Microsoft forum about it.

Use the Create PDF command in the Acrobat ribbon to use Adobe's technology to convert Word files to PDFs. There should be no such limits on that, assuming you have Acrobat.