I don't know how you believe you are not breaking copyright when you have used the books name in your title and also the copyright statement says "no part of the AIS Publications may be reproduced, stored in a retrieval system, transmitted, redistributed, republished or commercially exploited in any way without the prior written permission of Airservices Australia."
You are storing yours in a retrieval system (local cache) and you are commercially exploiting the documents as your application has no ability to view any other PDF's which would make it a general PDF viewer