You want to be able to secure the documents or device as well correct? Then I think currently your choices are Que or Irex 1000s . However I am not sure of the security of the Irex. One of the IRex users will post soon I'm sure.
You can annotate on either. The Irex is wacom. I actually wrote notes on the Que with my finger and the "soft keyboard" at CES You can "mark up" the document, scribble on the document or make digital "post its" that are stuck to the document all of which can be exported with the document.
Of course Brother also has the SV-100
http://translate.googleusercontent.c...DYlokbtib_Ldjg and the new sv-70
http://translate.google.co.uk/transl...n&hl=&ie=UTF-8 which are both large size ereaders with security in mind. The cost more than the Irex and are only being sold in Japan. I am sure tho that if you were going to order several for a board they would make a deal.
All have a "print to" function and Que has other wireless sync methods for document/email etc transfer
Que will be the most durable.
video showing the sticky note and other business doc uses of the Que
http://www.youtube.com/watch?v=NyPDjKhWQXM