There are some possibilities, under certain circumstances… The easiest is when you can navigate page by page.
One possibility would be an application-level JavaScript which contains two items which could be attached to the Tools pane (in Acrobat X and XI). The first item is used to open and connect the two documents. The second (and maybe third) would be used to do the scrolling.
The first step would be to define the two documents, creating doc objects using openDoc(). Let's call those objects doc1 and doc2.
In the second step we could do something like
doc1.pageNum++ ;
doc2.pageNum++ ;
and similarly to move back
doc2.pageNum-- ;
doc1.pageNum-- ;
Having the core code, we can now create the toolbuttons, which will be automatically added to the Tools pane.
If the documents do not have the same number of pages, we will get error messages We can prevent them using the try…catch statements.
Hope this can help.
Max Wyss.