Quickly convert HEIC to PDF for expenses submission

Recently I had to convert a large number of photographs taken on my iPhone into PDF for submission with my expense report. I took to my old faithful ImageMagick (installed via HomeBrew) and its mogrify command:

mogrify -resize 50% -format pdf -level 0%,100%,2.0 -type Grayscale -compress jpeg *.HEIC

Hope this helps!