I'm the founder, but you can use sysrev.com to review pdfs, json, text, etc. and assign labels / do annotations. You can see https://blog.sysrev.com/simple-ner/ for how to build something like a gene named entity recognizer in text. We have mechanical turk like compensation tools too, but you'll need to ping me ([email protected]) for access.

There are other options for this too, I think spacy.io has an annotation app.