Cryptographically sign the documents. It's a long solved problem.
It's a solution to a problem that most likely doesn't exist.
Luckily we've got a large-scale, decades-old real-world counterexample to the ISO model. It's the IETF model. IETF standards have been freely available to anyone and everyone for decades, and are posted and re-posted... well, let's take a security-critical standard that a good chunk of the Internet relies on and that you're using right now to read this, RFC 5246. Google gives 182,000 hits for that, of which some admittedly will be references, but lets say there's at least tens of thousands of copies of that floating around, including in .ru, .cn, and for some reason I'm not getting anything for .kp but I bet there's copies there too. They're plain text files that anyone with the most basic tools can modify as much as they want.
As far as anyone knows, there have been approximately, oh, zero cases of anyone posting maliciously modified copies of it.
The nonsense about "we need to keep control to prevent this imaginary threat from materialising" is nothing more than ISO (and similar) propaganda to justify their charging outrageous amounts of money for what other standards bodies provide at no cost. Unfortunately like other types of propaganda they've been shouting it for so long that some people now appear to believe it.
An update, just had a look at a copy on a random Russian site,
here, since there was a mention of "would you trust something from some site in Russia". This isn't the English original but a complete translation into Russian (try doing that with a paywalled standard), and seems to be the same as the English original. So with freely-available standards you definitely can now download it from a random site in Russia, and it's now translated into Russian, and the world hasn't ended because of it.