Picture annotation tools allow to add text and visual cues (arrows, circle, lines etc.) to pictures.
One of the most famous picture editing tool.
This is originally a free PDF reader, which also has annotation tools.
Edji is a collaborative annotation tool, which allows to annotate PDF, images and web articles.
Microsoft Teams is a proprietary business communication platform which can be used as a basic LMS.
Free and easy picture editing tool. Only on Windows.