How to shrink images in Indesign

InDesign InDesign: minimize file size

enjoy the meal !

the thread is already quite old - but I would also like to add my mustard

we recently had an indesign document (current version 7.5.3) with incomprehensible 2.25 GB ( bytes) - Save as did not affect any change - only that idml-export brought success! believe it or not only 45.6 MB (45,637,632 bytes)

I don't understand one thing:

... Boundary conditions are also saved in a file - i.e. work steps that can be revoked if necessary. ... This can mean that actions cannot be undone ...

to to saveand close there are no more old work steps available to me - why are they saved? and is there a "place" - where i can see these marginal data?

greetings kester