I tried the software search tool for that filename and got nothing back. I would check for it on your installation media for Call Manager. If not, call tac. You might want to report the documentation probelem either way.
Its currently called MCSbackup.3-4-31.exe. I think they went with the generic statement 'download the MCSbackup.exe' because they change this version periodically and you should use whatever the latest version of that file is.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.