In the search for a cms which will be the main feature — the user directory (in fact private companies). From the engine require the registration of new companies by the companies and the administrator.
Roughly every second
The ability to customize groups and privileges, access to different sections.
Approximately every third
As well as the ability to assign (send) individual groups the various documents directory (pdf, text, etc.).
Don't think of such a functionality anywhere (*this does not mean that it is not, just personally, I don't remember)
Advise in favor of a cms to navigate? Heard that Drupal CMS allows to configure something similar.
Drupal, Bitrix, DLE may even Joomla I know how most of this list