I've written a Java action that does this. Feel free to contact me and I'll share it with you. It was a proof of concept, but you should be able to tune it to your wishes.
As far as i know, you can't.
You could however try to create your own page numbers.
I.e. count the total number of pages that are going to be created on forehand and use that to create and set pagenumbers.
Don't know if this is possible in your case but it could be an option.
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