I want to save bookmarks in Okular. It should work with our Okular version and
our poppler version in openSUSE Leap 42.3.

The missing configuration is listed here in answer1:
https://unix.stackexchange.com/questions/123226/change-and-save-pdf-annotation-setting-in-okular

Problem 1: Bookmarks and annotations won't be saved in the pdf file with "Save
as..."

Problem2: The workaround with "Printing pdf" doesn't work, too. Annotations
should be added, but if you choose the new pdf, no annotations are added.
That's only a link to the old pdf file.

Ubuntu is using the same Okular version and it should work there (information
in forums). So it has to be a problem with openSUSE.

How it should work:
I want to save all annotations and bookmarks in the pdf file. So I can send it
to other people and they can use them. Both methods "Save as..." and "pdf
printing" should work with annotations.