We are sorry to hear that you have this issue.
As I understand, you have a web-site with the GroupDocs.Viewer on the one server, and documents on the another, remote Amazon server, correct?
First of all you need to perform a little investigation. It’s important to find out what is the reason of such latency. Please download this document from the Amazon server manually and put it to the machine where GroupDocs.Viewer is located, and then try to display it.
If 40sec-delay still be present, it means that the reason of such abnormal latency is in the GroupDocs.Viewer. In that case please send us the document, our developers will investigate it and will try to fix this behaviour.
However, if GroupDocs.Viewer will display the document that is located on the same machine noticeably faster, that 40 seconds, then that means that the reason is a slow internet connection. GroupDocs.Viewer cannot display the document while it is still downloading, because document, in contradistinction to video or audio, is not a streaming content. For removing this delay you should develop something like ahead-of-time caching, when required documents are downloading to the local server not in the moment when they are required by the end-users, but before this moment (for example, on the project startup). Ahead-of-time caching is also supported by the GroupDocs.Viewer, please investigate the article “Description of GroupDocs Viewer DocumentCache class”.