Test Design Specifications real examples

I have read the definition in a lot of places, including http://ift.tt/2nMCYwJ and I have seen the templates with the main fields to include, however, I still need a real example. So basic Scenario: Project: Conversion Website, and the features are: login portal, upload a file, convert file, download file, feature 5 ... feature 20. Should I create a Test Design Specification Document for each feature, so I will have 20 word or excel files each of them including (TD ID, feature to be tested, approach, test ID, Pass/Fail criteria)? Can I put them all in one spreadsheet? What are the commom practices testers follow?