pdftk input_file_1.pdf input_file_2.pdf output set_name_for_output_file.pdf
systemctl list-unit-files --type=service --state=enabled # List Services which are Started Automatically
sudo systemctl is-enabled nginx # Check Service Autostart State
sudo systemctl status nginx
sudo systemctl enable <name_of_service> # Enable Autostart for Service
sudo systemctl disable <name_of_service> # Disable Autostart for Service
sudo dpkg -i ~/tmp/google-chrome-stable_current_amd64.deb