It's actually not too bad. You can run a pool of soffice processes, but unless you really care about the startup time, I'd suggest running individual processes

It's actually not too bad. You can run a pool of soffice processes, but unless you really care about the startup time, I'd suggest running individual processes per job, which you can run headless from the command line. For the most part libreoffice does well, although at some point you'll start to discover the quirks in their rendering...