Originally Posted by
njkayaker
I think the copyright exists whether or not it is declared.
One reason this would seem to be the case is that it is easy to remove the declaration.
Copyright isn't automatic. The intent to claim copyrights has to be declared. Yes it could be removed, possibly exonerating a third party that can claim to be acting in good faith, but removing the claim doesn't nullify it.
In any case the copyright covers only the document itself, not the information itself. There would be no ethical bar to drawing up a new set of prints to the exact specs, but changing for example the placement of dimension lines, or paraphrasing footnotes.