I have a need sometimes for one document to be referenced in several subsite document library locations. Any ideas what the best approach for this is?
There are several other ways of doing this.
Use a Link To Document content type. This is used whenever you have a library, and you want the document to appear in several libraries. I usually pick the most general library to house the document in and then enable the "Allow management of content types" in the Advanced Settings of the Library Settings. Then add the "Link to Document" content type and add that content type in the menu to link to the URL of the desired document.
You can also use Link Lists. Post the document in a library, somewhere public, that everyone that can get to the links of the document can get to the referenced document as well. Copy the URL of the document, and paste it as a link in another site or subsite, in a "Link List" of your choosing or create a new Link List.
You could use the 'Send To' feature found on the context menu of your document. If you set 'Other Location' to another document library, SharePoint creates a symbolic link to that original document. When the original document is updated, SharePoint can update all 'copies' of that document as well.