pdf.js unable to locate libraries in Drupal 7
Step1: Download from here: https://github.com/mozilla/pdf.js

Step2: Download Windows installer: http://nodejs.org/download

Step3: Download &amp; Install: https://www.drupal.org/project/pdf

Step4: Add the install folder of nodejs, to your PATH variable, so you can call 'node' command from command line

Step5: Through command line, goto /sites/all/libraries/pdf.js. Type 'node make generic'

Note: Make sure that in your library folder you have the pdf.js folder named exactly to "pdf.js". Then inside of that extract the pdf.js files. It should look like this.