Thank you for that information.
However, the two questions that I asked have not been answered, so would you please remove the "solution" tick?
In the mean time I have installed Virtual Box from the software boutique and set up an openSUSE virtual machine (KDE desktop) with a "shared folder" between it and Ubuntu-Mate. It works well and solves the "pdfchain is broken" problem as the Qt GUI for pdftk works.
One thing I noticed when doing that, was that KVM installs the virtual machines to the root partition, while Virtual Box installs them in the "/home" partition. I don't know if that always happens or is due to my particular set up.
Hallo Mr. Horwell, are you perhaps able to answer the questions I asked? Many thanks if you can - its all about understanding you see.