I seem to be getting 404's trying to look at admin guides here: Oracle8i Release 8.1.7 Documentation
The broken links on that page and some related Release 8 pages should be fixed now, thanks to the efforts of the documentation production team and the internal OTN support group.
The original problems seemed to occur only with specific PDF links on those release-specific pages. The HTML links worked, as did various "View Library" links (and PDF and HTML links within those libraries). From a check of random PDF links, all the links seem to work fine now.