I have many eBooks as PDF from SpringerLink, which I use for research purposes. The eBooks have indeed a table of contents (with more than 50 entries sometimes), but unfortunately it is not clickable. The bookmarks in the PDF often do not cover the full table of content, or do not have any bookmarks, thus using books with more than 1000 pages can be quite annoying.
Is there a way to make the entries of the table of contents clickable refereing to the corresponding pages? In addition it would be also very comfortable if even the references could be linked somehow. I am thinking of some sort of links the hyperref package in latex creates.
This question is closely related to How to create clickable table of contents in a PDF? but since this was asked a few years ago I suppose there can be some new tools around. In particular I am searching for a solution which does not require any payment.