Hi GroupDocs Team,
It is not clear from your request why you need GroupDocs.Viewer (it seems that you are using GroupDocs.Viewer for .NET library) and what functionality you want.
GroupDocs.Viewer is designed to view (display) different types of documents in a browser without downloading them. When you are viewing the document using GroupDocs.Viewer, the document (which is stored and processed on the server) is sent to the client-side in form of HTML/CSS/images - this is the only format, which a browser can “understand” without requiring third-party plugins like Flash or Silverlight. However, GroupDocs.Viewer allows you to download the original document, if Viewer is configured to allow such operations (this is enabled by default).
From you description we see that you do not want to display documents within the browser, but do want to download documents from the server and open them in the native desktop application associated with the document type. In this situation GroupDocs.Viewer is useless to you, because you can download files from server using just the browser.
In fact, even if you are using GroupDocs.Viewer and want to download documents, GroupDocs.Viewer cannot help to achieve what you want because the browser is responsible for transmitting files from server to client, saving them on a disk, choosing the default application for opening them etc. So you need to configure your web-browser. Many modern browsers (like Chrome, for example) allows you to specify a path where document will be saved (they may use default path), or point a specific application at file types etc. This allows you to download documents faster.
If you will have more questions please feel free to contact us.