Add rel attribute with nofollow value.

app/helpers/documents_helper.rb

@@ -12,6 +12,12 @@ module DocumentsHelper
     Hash[Document.sources.map { |k,v| [k, Document.human_attribute_name("document.#{k}")] }]
   end
 
+  def document_link_url(document)
+    uri = URI.parse(document.link)
+    return document.link if uri.scheme == "http" || uri.scheme == "https"
+    "http://#{document.link}"
+  end
+
   def bytesToMeg(bytes)
     bytes / Numeric::MEGABYTE
   end

app/views/documents/_document.html.erb

@@ -3,7 +3,11 @@
     <%= document.title %>
   </td>
   <td class="text-center">
-    <%= link_to t('documents.buttons.download_document'), document.attachment.url, target: :blank, class: 'button hollow' %>
+    <%= link_to t('documents.buttons.download_document'),
+                document.attachment.url,
+                target: "_blank",
+                rel: "nofollow",
+                class: 'button hollow' %>
   </td>
   <td class="text-center">
     <% if can? :destroy, Document %>