How do I user UserMailer in Rails to send a file stored on AWS with CarrierWave?

The command File.read(file_url) in the code below won't work because I'm trying to pull down a file such as (example - file_url= 'http://ift.tt/1BMZPeL') which is not a file but a file on a server.

What do I need to change to pull down this file from AWS and send through UserMailer?

  class UserMailer < ActionMailer::Base
         def send_user_pages(user, file_url)
            @user = user
            attachments["user_pages.pdf"] = File.read(file_url)
            mail(to: user.email, subject: 'Your Pages')
          end
   end