Law of Demeter and data models?
For some perspective on the LoD, read "The Law of Demeter Is Not A Dot Counting Exercise".  In particular the part under the heading "I Fought The Law and The Law Won".

I think in this instance that pages, paragraphs and lines are very logical subcomponents of documents.  These each have different but related behaviour.  The each also serve different purposes.

Forcing the document to handle interactions with subcomponents will - as you say - lead to clutter (and more chance of introducing troublesome issues).

The big thing about the LoD is that it aims to reduce coupling.  However adding methods to Document doesn't really reduce coupling as you're still writing code that says "do x to line y" - you're just asking Document to do it for you.

Don't get me wrong, the LoD is useful.  But like all principles it has to be used correctly to stay useful.

(Funnily enough a similar question with a similar answer as been asked at SO.)

Conclusion

In short I don't see any benefit for you in talking to Document rather than it's contained Pages, Paras, &amp; Lines.  Frankly I don't think there's any ROI for you.