How to print to PDF completely silently and save the PDF to a predefined location in Mozilla Firefox?

I'm trying to print to PDF completely silently and save the PDF to a predefined location in Mozilla Firefox. I don't want to interact with any GUI, I want to be able to just press CTRL+P or click on Hamburger Print to print to PDF to the predefined location. I already tried setting the following options in about:profile , but it didn't work. services.sync.prefs.sync.browser.download.manager.showWhenStarting: False pdfjs.disabled: True print.always_print_silent: True print.show_print_progress: False browser.download.show_plugins_in_list: False browser.download.folderList: 2 browser.download.dir

Question by Adel M. on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.