“the below” vs “the following”

The below vs The following--The word, "below," properly functions only as a preposition or an adverb, neither of which can take the definite article, "the." However, the word, "following" can function as a noun or an adjective, both which can be combined correctly with "the."

Thus, the least invasive correction of the example you cited is: "The changes below will occur ..." Better yet is the phrase, "The following changes will occur ..."

Why do I maintain the latter phrase is better? Unlike the former, it handles the prospect that the text it introduces might appear on the next page or in the next column. Sequence is certain (following), but page orientation (below) often is not.

That isn't right. "Below" functions as a noun, too.
So "the below" means that which is below in the same way "the above" means that which is above.

Usage examples of "the above" are "none of the above" and "the above is Theseus's opinion" (William Blake).

Cf. http://www.merriam-webster.com/dictionary/below
and http://www.merriam-webster.com/dictionary/above

From a practical viewpoint, I favor "following" as being less, well, geographical.

I work for a printing company, and sometimes well-meaning people don't realize that "the below [points] " may well be more accurately described as "the points at right" once, say, their Word file is turned into a brochure.

To me, "following" implies position in the flow of the text, whereas "below" implies physically being under something.