We create all the documentation files in HTML format, because PDF is not efficient for changes tracking. You could save the online documentation into PDF using a browser.
I did the method told, and it seems I am only saving the particular page I am viewing. Saving the whole documentation would mean clicking on each individual page and pressing Ctrl+P?
I think a offline documentation is good as some environment which customers use, might not have Internet access to view the online documentation.
I hope in the future we will come up with something. Thank you for noticing.
You can download zip archive from https://github.com/RapidScada/scada then find ScadaDoc folder and open web pages locally.