Notes option/editable encounters within purchased Adventures only visible to owner

With a physical version of a module notes can be added within it in the margins as a reminder of things that worked/didn't work for a re-run of the module later.  Would it be possible to add a feature to owned modules that might link a post-it like thing at the DMs discretion.  Say I've created my own narration for what the characters see within a room for instance.  This way I can preset it and just copy paste in a PbP type forum for instance.  Sort of like how .pdfs allow for note in a side bar.  

I think the encounter adjustment might already be in the works a little to increase or lower the challenge, but the notes could also be useful for this as well.