The Question is:
Entire document was created in upper case and need to change to lower case.
The Answer is :
Use a DCL command procedure that opens the file, reads a record, runs
the text through f$edit specifying LOWERCASE, writes the record, then
loops back and reads the next record until End Of File is reached.
Use a text editor? With EDIT/EVE, for instance:
C (to get into screen mode, if needed)
There are undoubtedly many other ways.