I am searching for the materials showing the Watchtower changing the original content like or examples of the following.
I wouldn't go making this accusation to anyone who will take you to task to provide some evidence for it.
"The Preaching Work will be finished in the 20th century and never be repeated".
In the example you give, the change was made between the public rag and the BV.
I do not know of one instance where there is a change between the CD and the printed version. The CD always reflects the last print edition.
Plus ........ there are some very embarrassing statements made that are still included on the CD that would have been 'edited' if they were doing what some newbie 'apostates' accuse them of. If you want to rattle the brain of a JW, use those, rather than an accusation that you haven't got original printed evidence for.