Is there any protocols to identify what sort of document MS-408 is?

[ReneZ]

If the plaintext is all in lower case, one can add 1 to every hk by randomly changing half the letters to upper case.   

One can even raise every hk to the maximum, without changing the length of the text or the alphabet, by encrypting it with a Vigenère cipher with the 26-letter key ABCDE...XYZ.

True, but I would call changing half the letters, or all of them, a very significant change. 

Just spelling changes won't do it.