Adding Pages no longer an option as of January 01, 2016

US Passport Updates and Reminders
 
Adding Pages
As of January 1, 2016, adding pages to a US Passport will no longer be an option.  If you need additional pages you will be required to get a new passport. 
"The decision to discontinue this service was made to enhance the security of the passport and to abide by international passport sanctions."   US Department of State 12-10-2015
 
Deadline to submit for the low cost option of a 2 week turnaround time  Dec 16, 2015.   Rush service available after Dec 16, 2015.

http://www.scpassportandvisa.com/adding-pages--passport.html