How to add long instructional text on document of records

Summary:

I need to have a long instructional text for a specific document of record, and I can't figure out how.

Content (required):

I have tried using page composer to add a new text value, but that doesn't seem to work. I've tried using a DFF, but i'm being limited to 150 characters. I've read that 21A allows few DFF to have 4000 characters, but it isn't working for me. I'm hoping there has got to be a way to add some instructional text to a document? It's more of a disclaimer then instructional text that i need so whatever is the best approach.