SVN has a GUI front-end with good Windows integration: Tortoise SVN. Many of my colleagues swear by it.
Msofficesvn is a Microsoft Office plug-in that gives access to Tortoise SVN inside Office applications. OfficeSVN
adds icons for SVN operations to Office 2007. OOoSVN is a similar plug-in for OpenOffice.
With those tools, SVN is usable without requiring a command line. Administering the repository might require basic command line competence.
SVN does require some user training, but that has nothing to do with programming. Mainly, you have to get people into the habit of 1: update, 2: work, 3: commit; and you have to train them to perform merges.
A document management system that provides pure archiving without exposing conflicts will be easier to use. But that's because it hides the difficulties under the rug: instead of confronting users with conflicts, it silently loses data when a conflict occurs.
A workflow where people take a lock before working on a document is a lot more constraining, but can save headaches if they can't be taught not to panic when a conflict happens.
(Note that I have no experience of teaching nontechnical people to use version control — I'm interpolating from observed behavior with “manual” versioning, where documents are sent by mail to a person who is supposed to merge changes.)
