Ok so I got it to work.
I made a folder where I place all my secured documents. For the test I called it ruby.
In that folder I placed a file called test.doc.
I then placed a .htaccess file with the following command:
in the same folder.
When i went to the site, ie.
http://site.com/ruby/test.doc I got an Access Denied error as expected.
In MODX i made a resource with empty for template and called it Documents with an alias of doc.
I made the resource a container, published it, and saved it.
I created a new Static Resource (right-clicked Documents and clicked Create -> Create Static Resource Here) under the Documents container. I selected empty for a template (which seems then take away the Static Resource field). I gave the document a name of Test and an alias of test. I went to the Settings tab and noted that I hadn't yet created the applicable Content Type. So I saved the document.
I went to System/Content Types and added a Word content type. I called it Word, with a mime type of application/msword and an extension of .doc and saved it. It's probably a great idea to input all the content types you are using now.
I went back to the Static Resource document I'd created earlier. In the Static Resource tab, I pointed the Static Resource field to my document (ruby/test.doc).
I went to the Settings tab and selected Word as a content type. I placed the document in a Resource Group (called members incidentally). I saved the document.
I went to the site and logged in with a user who has access to the members resource group and went to the url:
http://site.com/doc/test.doc.
I got the file. I confirmed I cannot get to this file if I am not logged in via direct URL and even when logged in I cannot get to where the file actually is, at /ruby/test.doc.