The lack of information is due to primarily 2 things -
First, Kabar has changed hands several times.
Initially, it was the Tidioute Cutlery Company and formed in 1897 in Pennsylvania (Little Valley??) and owned by a bunch of businessmen. It went bust around 1900 and the assets were bought by the Brown family in 1902. It moved to Olean NY in 1910. The Brown family subsequently sold the company to some Olean businessmen in 1961 who then sold it to some more businessmen who ran it into the dirt and filed for bankruptcy. Kabar assets were then bought by the Robinson Knife Company, who then sold it to Cole National in 1966. Lots of turnover in a few years.
Cole moved the company HQ from Olean to Cleveland. When Cole filed for bankruptcy in 1982, Kabar was sold to American Consumer Products and the HQ moved to Solon OH.
In June of 1996, ACP sold Kabar to ALCAS, who moved the HQ back to Olean.
Every time the company filed who owned the Union Razor/Union Cutlery/Kabar name filed for bankruptcy, or just outright sold the company, documentation was lost, either trashed by the new comers, allowed to rot/get eaten by bugs and rodents, or dumped due to not wanting to pay to ship paper all over the place.
Second - As to a lack of sales brochures and catalogs loose in the wild, dealers trashed the old catalogs when new ones came in. That's why that stuff is so hard to find. Both sides of my family had retail businesses for over 50 years. They never kept a single old catalog for the products they sold. I know when my father retired, I hauled at least 2 pickup loads of "current" catalogs, brochures, advertising literature to the dump. Farm implements, garden tools, fertilizers, pet supplies, paint, seeds, you name it, we sold it. If my father had been the pack rat I am, it probably would have taken an 18 wheeler to haul all the old stuff off.
Gunsil on BF probably has the best collection of old Union/Kabar material in the world and he doesn't have anywhere near all that was produced. And he's been scrounging for it since dirt was clean.