The paradox of Schrödinger's cat, suggests that the state of the system is in superposition until it is observed. And the Heisenberg uncertainty principle suggests the act of measurement disturbs the state of the system. So your statement, ("the act of acquiring information (observing or measuring) alters the information content of the system"), seems to be in alignment with them.

But is it valid to replace the "state of the system" with "information content of the system", as you put it? This is a slippery area for me. Do you know where can I go to learn more about information vis-a-vi entropy?