Zander,
I have a similar situation here building molds for our customers. Typically when we complete a mold, we like to burn all of the CAD files to a CD and deliver it with the mold, with all of the drawings at Rev1 (released status). Sometimes this "slips through the cracks" and doesn't get done. And, it is fairly common that a mold will return to us for some "tweaking", an engineering change, or repair due to damage. A lot of time this requires some minor design changes which changes the revisions of several of the drawings.
So, how does the customer know what revision the tooling drawings are, at any given time? They could call us any time they needed to know (which is a hassle), or they could look it up themselves. I have setup an ftp site with different folders for each of our customers. Each of our customers have a login/password that gives them access and visibility to THEIR folder only. Under each of the customers there are subfolders for any of the molds that we have built for them.
I use Ipswitch WS_FTP Pro software to automatically update the entire ftp site every night with the latest PDF files for all drawings. When we make a new revision to a drawing, all we have to do is remember to create a new PDF and it will be posted on the ftp site that night for customer access. This could be done with the CAD files themselves, but as you know CAD files can get quite large.
This does take a bit of planning and time to setup. But we charge them a nominal amount each month to "host" their drawings for them. This is obviously optional. But it does make it worth the time.
Hope this helps...
P.S. We originally set this up this way because we have this one customer that will be building many manufacturing/assembly lines around the world consisting of our tooling design. Unfortunately, we will not be able to build all of the tooling for every location due to politics. So they wanted other locations around the world to have access to the latest drawings 24 hours a day for obvious reasons. If we had left it up to our customer to supply the different locations with the latest drawings, we would have lost "control" of our design. Any changes that we wanted to make would have been forbidden without first getting an engineering change request approved from them. This sometimes takes weeks with a company this size. With us controlling the drawings via ftp, we remain in control of the design. This is a very large project with roughly 800 tooling drawings that I have created and control.