Text Annotation And Highlighting Library – Annotate.js
A mobile-friendly text annotation JavaScript library that allows you to highlight text and attach notes (comments) to it.
JavaScript & CSS Text Annotation
Simple Text Annotation JavaScript Library – Annotations.js
A zero-dependency JavaScript library for annotating text within your document using the normal button element.
Animated Handdrawn Text Annotation Library – Rough Notation
Rough Notation is a fancy JavaScript library for annotating your text with animated, sketchy/hand-drawn styled graphics using Rough.js.