How can I update a module to a specific version using Drush?
By default, drush pm-update will update Drupal core and all enabled projects to the latest recommended releases. The optional project argument allows you to provide a list of installed projects to update, thereby limiting the scope of the update.
You can also pass a specific version of Drupal core as a project argument and Drush will limit the upgrade to that version of core (and core only, unless you pass other projects along as arguments.)
drush pm-update entityform-7.x-2.0-rc4