I will toot the hypothes.is [0] horn again. It is possible (if sometimes finicky) to use it to annotate pdfs. See for example a demo annotation [1]. The other r

I will toot the hypothes.is [0] horn again. It is possible (if sometimes finicky) to use it to annotate pdfs. See for example a demo annotation [1]. The other really cool thing about this is that hypothes.is fingerprints pdfs and uses a URN to uniquely identify them, so you can annotate a local copy of a pdf (in the browser) and those annotations will show up on any other copy of that pdf anywhere on the internet. 0. https://hypothes.is/ https://hypothes.is/ 1. https://hyp.is/hZbgFO_ZEeemmt9kojvZIA/arxiv.org/pdf/1712.10027.pdf https://hyp.is/hZbgFO_ZEeemmt9kojvZIA/arxiv.org/pdf/1712.100...