Currently Being ModeratedNov 15, 2012 12:51 PM (in response to Xrubyxbabyx)
Powerpoint has add-inns that have mark up features
There are numerous applications for Mac OS X
I have no information about iPa, I dont have one
Since this is the Keynote for Mac discussion it would be more appropriate to post your queryin the Keynote for IOS discussion group.
In the meantime, Google "annotation" or "mark up" for iOS and see what comes up.