Update (11/01/2017): A FREE demo version of this tool is now available here.
It can be used to test it out, but it only contains the "Scroll Down" command.

Another New Feature: You can now easily align the viewing position of all the open files with the active one.

New Feature:  The tool can now scroll any number of open files, not just two, as requested.

Comparing PDF documents side by side is a common DTP task in Acrobat or Reader, but the problem is you can't scroll two documents at the same time, so keeping them aligned can be difficult and time consuming.
That is the reason I've developed this new script which allows you to keep your documents in perfect alignment while you review them.

You can select the scrolling offset (in points) and then scroll both documents up, down, to the left, to the right, or skip pages forwards or backwards, all in perfect sync.

The windows themselves can be arranged at whatever configuration you find most comfortable, and can even be placed on different monitors.

IMPORTANT: This script does not allow you to synchronize the scrolling of the files using the mouse or the keyboard arrows directly. It only works through the buttons that it adds to the interface of the application.

After installing the script, the new scrolling options are available under a new sub-menu under the Window menu, as well as under the Tools menu (or toolbar, for easy access):

(click to enlarge)

And after using the Scroll Down option, the documents have simultaneously scrolled and now look like this:

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