Exporting a drawing to pdf looses highlighting.

I’ve opened a pdf document in LibreOffice to Highlight some of the text and make a couple of changes.

If I save it as an .odg all is saved. If I export it to a pdf, the changes are there but none of the highlighting.

What am I doing wrong?

Update. I’ve now found that the problem exists in the Linux version but not in the Windows version so I’m going to close this and open a bug report instead.