It would be useful if any document (single document, or one on a documents page) could have a text page attached for the addition of notes or comments.
For instance, a retrieved historical document where you could explain that the document is incomplete, or add some context, or explain why this document has been retained (i.e., its utility). This could be accessed by right-clicking on the document, and when a document has a note attached, a symbol would indicate that fact. Essentially, this would be like a note paperclipped to a physical document.