Error: iOS Viewer crashes when viewing a document

The main reason for this is due to hi-res, badly formatted PDF documents with unused attachments and hidden layers that are then converted to PDC format.

Ask the Publisher of the document to optimize the PDF by saving it as PDF version 1.4 (Acrobat 5 compatibility).  This will remove all the unnecessary code.  In Acrobat Pro this option can be found from the File menu > Reduce File Size > Compliance with earlier versions.