Document resource route with the option of scoping by version

rake routes

GET    /documents/:id(/:version)(.:format)                            {:action=>"show", :controller=>"documents"}
GET    /documents/:id(/:version)/edit(.:format)                       {:action=>"edit", :controller=>"documents"}
PUT    /documents/:id(/:version)(.:format)                            {:action=>"update", :controller=>"documents"}
DELETE /documents/:id(/:version)(.:format)                            {:action=>"destroy", :controller=>"documents"}
GET    /documents/:document_id(/:version)/sections(.:format)          {:action=>"index", :controller=>"sections"}
POST   /documents/:document_id(/:version)/sections(.:format)          {:action=>"create", :controller=>"sections"}
GET    /documents/:document_id(/:version)/sections/new(.:format)      {:action=>"new", :controller=>"sections"}
GET    /documents/:document_id(/:version)/sections/:id/edit(.:format) {:action=>"edit", :controller=>"sections"}
GET    /documents/:document_id(/:version)/sections/:id(.:format)      {:action=>"show", :controller=>"sections"}
PUT    /documents/:document_id(/:version)/sections/:id(.:format)      {:action=>"update", :controller=>"sections"}
DELETE /documents/:document_id(/:version)/sections/:id(.:format)      {:action=>"destroy", :controller=>"sections"}
GET    /documents(.:format)                                           {:action=>"index", :controller=>"documents"}
POST   /documents(.:format)                                           {:action=>"create", :controller=>"documents"}
GET    /documents/new(.:format)                                       {:action=>"new", :controller=>"documents"}

routes.rb

  resources :documents, :except => [:show, :edit, :update, :destroy] do
    member do
      get '(/:version)', :action => :show
      get '(/:version)/edit', :action => :edit, :as => :edit
      put '(/:version)', :action => :update
      delete '(/:version)', :action => :destroy
    end
    resources :sections, :path => '(/:version)/sections'
  end

Is a version mapped to a real piece of data in your database? You don't have to have a table to have a resource, even one you want to nest. So you could nest a version resource within your document resource, then use the :id param to find the version of the document you want to view. The alternative that comes to mind is to just have the version be a parameter at the end of the URL, like ?version=xyz, and then check the params hash in your controller. You can create links to the versions using

link_to @document, :version => '1.0'