LayoutWindow to get and set view bounds
With LayoutWindow.bounds I can get and set the bounds of the window, but I want to get and set the bounds of the view port, ie. what the user sees inside the window. If view port bounds is too difficult, then just a centerOfView coordinate would be fine—combined with the already-available zoom value, that would achieve most things I'd need.
For what it's worth, it is possible to do what I want in Illustrator.

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Nicolas Carrieres commented
I've spend the last week looking for a way to do exactly what m1b is describing, being able to reference the active viewport would mean that one can create a script to easily compare several documents without needing to export the files on pdf first to check them in Acrobat.