The most famous change is the January 1st 1989 Watchtower "preaching work ending in the 20th century" quote which was changed in the bound volume http://thegoverningbody.org/watchtower-magazine-lies-governing-body/
There have been a few other changes , mainly in the artwork , often when the WTBTS pinched pictures from other publications - eg the Johnnie Walker incident. http://www.cftf.com/online/1998AprJunp06-07.html
But generally the bound volume remains unchanged. I checked the latest CD Rom wondering whether the ludricous experience of the Ethiopian teenager being offered a 3,000 euro a month salary had been revised but it is still there. To me , this shows the basic dishonesty of the WTBTS in not admitting a mistake & changing it.
w115/15p.12par.5ChristianFamilies—“KeepReady”
What good results there can be when children are trained to keep a simple eye! Consider the example of a teenage girl in the country of Ethiopia. She did so well in her schoolwork that upon completing her basic education, she was offered a scholarship for further education. Having her eye focused on serving Jehovah, however, she turned down the scholarship. Soon thereafter, she received a job offer that would pay her 3,000 euros a month—a high amount in comparison with the average wages in her country. But the girl’s “eye” was set on pioneer service. She did not need to consult her parents to turn down the job. How did her parents feel on learning what their daughter had done? Why, they rejoiced with her and told her how proud they were of her!