PDF Mix Tool is an open-source and lightweight application allows to split, merge, rotate and mix PDF files.
The software is written in C++ and depends only on Qt 5 and PoDoFo.
The software offers official snap (containerised software package) package, so it can be easily installed from Ubuntu Software:
You can also run command in terminal instead to install the snap package:
snap install pdfmixtool
For Ubuntu 16.04, install snapd daemon if previous command does not work.
sudo apt install snapd snapd-xdg-open
PDFMixTool did not seem to work for me:-) However, one called PDFMixTool from software center worked well.
snap store could not be contacted.