PD / copyright for new editions

[poco.allegro]

I wonder what is the exact law when we talk about new editions of PD-music.

1. New edition of Bach, plain Urtext, newly engraved.
2. New edition of Bach, with fingering, slurs and other addons.
3. New edition of Bach, scholarly edition, with introductory text.

The concert question: when it is free to scan a new edition and upload, or print freely?
Thanks.

[coulonnus]

Read Urtext editions in https://imslp.org/wiki/IMSLP:Copyright_Made_Simple and https://imslp.org/wiki/Public_domain