Thanks for the confirmation.
Unfortunately, responsive behavior of the viewer container is not implemented in the open source document viewer applications. Also, there are no builtin scripts available to achieve this feature. However, I am logging a request to check if there is any possibility to make the viewer responsive. You can follow this link
for further updates related to this issue.
of GroupDocs.Viewer for .NET by making a pull request.
In case of any confusion, please feel free to ask.