Various commands.

Install .deb files

sudo dpkg --install packagename.deb

Print from command line

lp filename

Restoring deleted files

trash-restore filename

Combine two pdfs to one

pdfunite file01.pdf file02.pdf output.pdf

Downloading a video in best quality

youtube-dl -f 'bestvideo[ext=mp4]+bestaudio[ext=m4a]/best[ext=mp4]/best'