Bulk convert with ImageMagick

The following might be useful if you scan some images and want to convert between formats.

Use mogrify from the ImageMagick package in order to convert more than one image at once from one format to another.

From PDF to JPG:
mogrify -format jpg -quality 80 -density 300 *.pdf

From JPG back to PDF:
mogrify -format pdf *.jpg