```ruby
module PdfjsRailsEngine
  class Engine < ::Rails::Engine
    isolate_namespace PdfjsRailsEngine

    initializer 'pdfjs-rails-engine.assets.precompile', group: :all do |app|
      app.config.assets.precompile += %w(
        pdf.js-gh-pages/web/viewer.css
        pdf.js-gh-pages/web/l10n.js
        pdf.js-gh-pages/web/viewer.js
        pdf.js-gh-pages/build/pdf.js
        pdf.js-gh-pages/build/pdf.worker.js
      )
    end

    initializer 'pdfjs-rails-engine.assets.paths' do |app|
      app.config.assets.paths << File.expand_path("#{root}/lib")
    end

    # initializer 'pdfjs-rails-engine.load_static_assets' do |app|
    #   app.middleware.use ::ActionDispatch::Static, "#{root}/vendor"
    # end
  end
end
```

Update path to static assets
user
```ruby
module PdfjsRailsEngine
  class Engine < ::Rails::Engine
    isolate_namespace PdfjsRailsEngine

    initializer 'pdfjs-rails-engine.assets.precompile', group: :all do |app|
      app.config.assets.precompile += %w(
        pdf.js-gh-pages/web/viewer.css
        pdf.js-gh-pages/web/l10n.js
        pdf.js-gh-pages/web/viewer.js
        pdf.js-gh-pages/build/pdf.js
        pdf.js-gh-pages/build/pdf.worker.js
        pdf.js-gh-pages/web/images/*
      )
    end

    initializer 'pdfjs-rails-engine.assets.paths' do |app|
      app.config.assets.paths << File.expand_path("#{root}/lib")
      config.assets.precompile += %w(vendor/assets/images/*)
    end

    # initializer 'pdfjs-rails-engine.load_static_assets' do |app|
    #   app.middleware.use ::ActionDispatch::Static, "#{root}/lib/web"
    # end
  end
end
```
assistant