Annotator
Annotator allows you to add annotation functionality to any webpage.
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Free
Annotator is an open-source JavaScript library to easily add annotation functionality to any webpage.
The app can have comments, tags, links, users, and more. This program also fosters an active developer community with contributors from four continents, building 3rd party plugins allowing the annotation of PDFs, EPUBs, videos, images, sound, and more.
DOWNLOAD
Free