True, we get plenty of high-res pictures of film in PDF here and some of them are ridiculously large, easily approaching gigabyte sizes, like you said. But that's more a problem of the user creating the PDF than inherent to PDFs. A raw 36 megapixels (our fancy 4K displays are only 8.3 megapixels, for comparison) picture reproduction of an ISO 400 film takes only about 70 MB, which tells us that something went wrong in the transfer if a PDF containing 10 pages of them cracks 1 GB.
So, yeah, there are these monsters that send even beefy computers thrashing. But in my experience something in the creation process went wrong and it is appallingly common for a trade where PDFs are the go-to transfer format (I'm looking at you AutoCAD users!) I'd guess that the archive is doing the same we do, reprocess them for sensible results and store them. I assume you think the archive does not and then I'd agree with you. One determined civil engineer with AutoCAD can fill 8 TB in a week ;)
So, yeah, there are these monsters that send even beefy computers thrashing. But in my experience something in the creation process went wrong and it is appallingly common for a trade where PDFs are the go-to transfer format (I'm looking at you AutoCAD users!) I'd guess that the archive is doing the same we do, reprocess them for sensible results and store them. I assume you think the archive does not and then I'd agree with you. One determined civil engineer with AutoCAD can fill 8 TB in a week ;)