TOPIC:

How to change the z-order of selected annotation to bring it to front of all other annotations?

There isn't any direct way to do that.
Actual PDF definition says annotations are rendered in a sort of FIFO way without priority or depth.
We should think about flow like that below:
- select original annotation
- create a new copy on the same page
- delete the old one

That way the new annotation will be on the higher level.
It should work with two annotations, but what's would happen with three, four or more annotation looking for a way to reorder depth not playing only with higher and lower level?

Actually I took a look at Foxit editor and Acrobat Pro and wasn't able to find such a feature even on that huge take of code.
If you think I'm missing something, please let's me know and put your suggestions here.

We will try to discuss about your request and give you a more exhaustive feedback as soon as possible.