No, disappointingly there are not. It really bothers me when large PDFs aren't bookmarked. This should be standard practice.
https://www.reddit.com/r/rpg/comments/lmskkw/electric_bastionland_pdf_no_bookmar...https://gist.github.com/tuirgin/88ab0641931d6d1770c82c6d7f8e7c44
Following this I was able to get bookmarks added to my PDF.