Im not on desktop so this is more of a guess than an actual solution but Ill try to make it easy to understand.

They have what looks like a rendering filter over the javascript (docs are loaded with JS so JS blocking doesn't work.) So in theory they have the source file linked in the javascript so if you find that link to the file, you can do that using the inspecter tool. you could download it using something like wget.

Another option would be google dorks as they may have made some files accidentaly public.

filetype:pdf site:"doccity.com" intitle:"file name your looking for"