Whatever it was, apparently it was VERY expendable.
This reminds me of one of my friends over on the MyOpera Community.
She loves to constantly be trying out new Linux Distros. She's still learning how to navigate Linux World so she one time inadvertently did something wrong and wiped out 31 Gig of SOMETHING. She was like, "Well, I don't know what I wiped out, but as far as I can tell, everything seems to be working." I go, "WHAT? You wiped out 31 Gig of something and can't see anything NOT working? If I wiped out 31 Gig, I'd have a nonworking computer ... especially since my Hard Drive is only 10 Gig."
So yeah, it's difficult to believe Adobe Reader just shed 20 Meg and we probably wouldn't even notice a difference with its functionality.