In my understanding Selenium Webdriver can handle the starting of a download. Then the used browser will download the file and store it to disk.
Further handling of the file depends on the configuration in your operating system and how given file types are processed or read. This should be out of reach of Web client testing tools such as Selenium or Testcafe.
For doing more testing you may consider using Robot Framework that has broader testing functionality and is NOT restricted to the browser. Robot Framework may use Selenium through an adapter module and may do additional checks and actions with downloaded content.