A PDF is a set of objects with a cross-reference table or xref stream at the end. When the table is damaged, readers scan the file for objects instead, which is why a corrupt PDF can still open and why a linearised PDF loads its first page before the whole file has downloaded.
Use qpdf to rebuild the table and to linearise a PDF that is served over the web.
Where this came from
Notes like this one come out of the file library rather than out of a release schedule. The pages linked above are the entries that were being worked on when the note was written, and those entries are rebuilt with each release of the toolset, so a note can go out of date in a way a format page does not.
When that happens the note stays where it is and gets a correction at the bottom rather than being rewritten, because the point of most of these notes is the order things were tried in. The editors who write them are the ones who maintain the catalogue.