If you refer to one of the manuals like this (link), then it is not the correct one, simply due to it being outdated and explaining a web interface of legacy firmware.
Here lies a problem: current RutOS is being actively developed, new features are added and changes to the current web interface also are implemented with almost each subsequent firmware release. This makes it very difficult to generate and manage new .pdf manuals, that is why you will not find one.
The best way to access most up to date manuals and information is to refer to the previously mentioned wiki pages, as they are continuously being updated.
Best regards,
