Hello. The file mimeinfo.list apparently overrides mimeinfo.cache which seems to be recreated upon installing/upgrading packages.
Creating the following file: [Default Applications] application/pdf=okularApplication_pdf.desktop as mimeinfo.list under ~/.local/share/applications/ or /usr/share/applications/ (as per user or global requirements) helped for me. Source: https://www.ryananddebi.com/2014/09/29/linux-fixing-pdfs- opening-in-gimp-in-firefoxzotero/ which refers to https://wiki.debian.org/MIME I confirm that this works for me on Kubuntu Bionic LTS with latest updates. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/574342 Title: GIMP set as default pdf viewer To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gimp/+bug/574342/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs