Overview

This solution will combine 2 or more PDF’s into a single file. It operates from the command line with nothing more then GhostScript installed from brew on macOS (or your favorite package manager on Linux).

Details

Install Ghostscript with brew:

brew install gs

Combine the PDF’s with GhostScript:

gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=merged.pdf kc3-2020-obj1.pdf kc3-2020-obj2.pdf