There is a good chance the documents are covertly marked as
   you suggest, the ostentatious classification markings a ruse for
   untutored yokels to fancy are genuine.
   Covert markings have been in use for a long time, as well as
   ostentatious markings. On paper as well as digital and other
   forms of electronic.
   And certainly packets carry unique markings in a variety of
   overt and covert types.
   Some of the techniques fall under the inadvertent emanations
   rubric associated with Tempest -- which has blossomed well
   beyond the FOIA releases from the late 1990s. TSCM is a
   marvel of duplicity and ruse.
   At 08:16 PM 5/13/2014, you wrote:

     From: Black Fox <fox@vbfox.net>
     On Tue, May 13, 2014 at 2:58 PM, coderman <[1]coderman@gmail.com>
     wrote:
     > On Tue, May 13, 2014 at 1:00 AM, John Young <[2]jya@pipeline.com>
     wrote:
     >> > We've seen the Greenwald book No Place to Hide, where are the
     >> > promised gush of Snowden documents available? His publisher
     >> > doesn't show a source. Surely not another marketing tease.
     >> great question; let us know if you find them!
     >[3]
     http://glenngreenwald.net/pdf/NoPlaceToHide-Documents-Compressed.pdf
     If I were the telephone company from which the records were
     requested, I'd note that the records were requested in "electronic"
     format.  Then, I'd ask a programmer to write a program to write a
     program to generate pdf files with embedded "captcha"-type text:
     Images that are quite apparent to the human eye, but are very
     difficult for any computer to make any sense of.   All the phone
     records would be there (in no particular order), and they'd all be
     very readable to humans, but...
                    Jim Bell

References

   1. mailto:coderman@gmail.com
   2. mailto:jya@pipeline.com
   3. http://glenngreenwald.net/pdf/NoPlaceToHide-Documents-Compressed.pdf