Which application can be recommended to save a whole site recursively off line?
SiteSucker is a great tool for this. They have both a Mac version, and a iOS version. I have used the Mac client a while ago.

If you want to do this on the computer, 'wget' is a great tool, and the -m flag will help you mirror the site to a local directory. You may have to install wget through homebrew or another similar tool.