Is drupal for my company ?

Hello,

I have to build a web site for my company and I'm looking for a CMS. Drupal seems very good, but I have a question about it.

My company has external collaborators and we would like to use our web site to exchange some informations (general information, technical reports). But we don't want members of one project to have an access of the documents of an other project. Can I set an access (read content / post article) for a group of users on a special section ?

Best.