Skitch can annotate any graphic file - it will open JPG, PNG, PDF, TIFF, EPS… So now it’s not just a screen-grabbing utility, but an image-commenter, which puts it in a different place to Snapz et al.

Perhaps my favorite addition to Skitch are the improvements made to shapes. By simply holding the shift key, you can draw perfect circles and squares, while arrows and lines will snap into place at 45 ...