Does it have to be a Permanent Sign?

This should comply. I would just include a narrative that says that the stand is placed so all building visitors and occupants can see it.

Can it be digital signage as part of a digital kiosk within the main lobbies that all visitors will engage with?
Thanks

No. How would visitors outside of the building know not to smoke near doors, operable windows, and outdoor air intakes?

Per a literal reading of the rating system text (and without checking Interpretations or Addenda), the signage must achieve one of the following:
1. Allow smoking in designated areas,
2. Prohibit smoking in designated areas, or
3. Prohibit smoking on the entire property.

It is implied, but not clear from the rating system language, that smoking within 25 feet of openings be similarly prohibited with signage.

Assuming signage must both achieve one of the first 3 options, and additionally prohibit smoking within 25 feet of openings, it is further implied that visitors should be exposed to signage before they would otherwise enter an area where smoking is prohibited.

I don't think there is anything which would require building mounted signage, although movable signs could (and probably should) be questioned by the certification reviewer, and signage mounted only indoors would obviously fall short of being visible to visitors prior to entering non-smoking areas.