Isn't that almost same as current pdf embed plugin in OJS, it just say client system to run Adobe plugin and display document. Problem is that you cannot control Adobe Reader plugin, so you can't disable printing, downloading and further sharing of documents, and that could be a problem to some institutions that have to obey to local country copyright, for example, I'm working as digitizing assistant at Faculty of Philosophy, University of Novi Sad, Serbia and our Law say that schools universities, faculties and other educational institutions can use any publication or part of it for educational purposes, and that means that institution can digitize some journal that is copyrighted, put it in repository for students so they can read it, but institution must not allow further reproduction, copying and distribution of that journal. If we use Adobe Reader as plugin for displaying files we are directly violating the law because it allows all of that, in pdf.js you can modify file viewer.html file and define what functions and buttons are available for end users. In my project, digital library i have done that in Drupal and result is that users can read publications, system remembers last viewed page for them, they can copy text from files, but they can't copy entire file and share it further. You can see demo version of system at address http://www.digitalnab.tk
, to access publications you have to click on button PRIJAVA and enter gost in first and second row (username and password) and then click Prijavi se. After that you can add node/1 after .tk/ in address bar to go to content (it will take some tome to open file because it has 636 pages).
And of course one more important thing about that is that nor webmasters nor users are dependent on local Adobe reader or any other installation on local machine, I have tested it on windows and linux pc, and allso on different smart phones and tablets and it is working without updates or any kind of instalations or upgrades.