I wonder how it would do with the djvu codec which tends to have been used specifically for archiving documents. I suppose it is best applied at source if the physical material is at hand.
Might still be worth taking a look at as an experiment since this codec separates text, background and images into different layers, even when converted from another format.
Found the following zoom levels:
0. byte (Deep Zoom Image) (868480 x 453747 pixels, 376956 tiles)
...
I think, I'll skip downloading this