> ... to set bookmarks for PDF when doing a save as PDF on the book.
> This works for all FO_PgfFmt's defined in the document except when
> the FO_PgfFmt is defined in a master page. Is there some setting that
> is needed to get bookmarks from master page FO_PgfFmt's?
I'm not familiar with this API, but you appear to be seeking to do something that is impossible.
Master Pages, per se, never exist in a rendered PDF, so no functional link can point to one.
Master Pages are used to generate body pages, but a PDF could have multiple instances of the same MP, which would result in multiple targets for links, so no attempt to do so is made during PDF generation (even if your document has only one such MP present).
Reference Pages are a similar situation. You can actually have a cross-reference to RP content, and it renders as a hypertext link in the PDF, but goes nowhere when you click on it.