It should be stated here that unless you've worked with Content Management Systems before, you will probably find any proposed solution overwhelming.
There are a number of free and open source systems out there that allow you to manage and monitor changes to documents, resources, templates and what have you. But the problem is that they all do much more than that, including user management, role assignment, integration with other platforms and applications, and so on.
By the way, every recent Windows license comes with a free version of SharePoint Foundation, which contains just about everything you need for basic Content Management. There's a learning curve, however.
I'm sorry for appearing to be so vague, but I really can't give you a more precise answer. You'll have to do a bit of investigating by yourself and determine how simple or complex of an implementation your organization requires.
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Technical Product Manager
I don't want to achieve immortality through my work; I want to achieve immortality through not dying - Woody Allen