The question sounds pretty trivial, but an additional complexity is introduced by the fact that the documents are generated non-deterministically on the file share. In addition, there is a requirement to make the box hosting the physical folder being shared; send a message to the SharePoint server that the document is done being generated, after which point the download occurs, followed by moving it to the document library (this post-message process I can handle)
There are multiple situations involving scenarios that require messaging such as these. Would my client be a good candidate for an Enterprise Service Bus (or is that overkill?)