I'm not familiar with this as a limitation of the N800 pdf reader (I just don't know one way or the other) but people talk about evince -- maybe that would read it. Alternatively, you ought to be able to get past the problem by decrypting it on your desktop. See, e.g., http://www.cs.cmu.edu/~dst/Adobe/Gallery/ and http://www.guapdf.com/ and, of course, you can google for more, similar solutions.