I have already discussed this in discuss.kde.org https://discuss.kde.org/t/okular-and-attachements/26499/7 SUMMARY when a pdf contains a link to an attachment (the attachment embedded in pdf), when you click on the link you are only offered to save it and not to open it. Other programs open the file (atril, AdobeReader, Foxit) STEPS TO REPRODUCE 1. Get a pdf file with attachment. Eg http://myria.math.aegean.gr/~atsol/tmp/test.pdf 2. Open with okular and click on the link (Click me! in the above pdf) 3. Alternatively, right click on the link. OBSERVED RESULT (Left) click opens the save dialog. If right click the menu does not offer to open the attachment. Only save it. EXPECTED RESULT With the (left) click okular should open the attached pdf either in new window or in tab (depending on user preferences) Right click menu should show an entry to open the attached pdf. SOFTWARE/OS VERSIONS Windows: macOS: (available in the Info Center app, or by running `kinfo` in a terminal window) Linux/KDE Plasma: KDE Plasma Version: KDE Frameworks Version: Qt Version: ADDITIONAL INFORMATION
Did you create that file yourself? Can you create one that has a random file (let's say a libreoffice calc file) instead of a PDF? I'm interested in checking if the other apps still just open it or suggest to save.
I have re-created the test.pdf file at http://myria.math.aegean.gr/~atsol/tmp/test.pdf to include pdf, png, odt, doc,ods,xls and the tex source too. atril (from MATE desktop) still open all attachments properly (png with eom, odt with libreoffice etc) Still okular only suggests to save the attachments.