If you use SMEStorage (a cloud storage aggregator) you can add DropBox as a client. Unlike DropBox SMEStorage has WebDAV, so the iPad can both import and export directly too it.
The downside is that SMEStorage isn't very good at updating files that are added directly to DropBox (like through you computer's synced folder). You can get around this by getting the iSMEStorage app and forcing a refresh.
There is another service DropDAV which adds WebDAV access to DropBox. Unlike SMEStorage it has a monthly fee. If you're a pro it might be worth it.
Box.com is another cloud service. Unlike DropBox it has WebDAV so it's easy to use with Pages. Also unlike DropBox there is no (free) sync utility for the computer, so you have to use a browser to access and sync your files on that side.
I do not know of a perfect solution at this time. Everything requires at least a little workaround on one end or the other.