This one allows you to highlight lines in a PDF. Actually made for my wife, who loves to knit: the app helps to maintain focus on a specific part of a pattern.
Links:
- Main application: https://j0r1.github.io/HighLite
- Help: https://j0r1.github.io/HighLite/help.html
Your feedback is always welcome at jori.liesenborgs at gmail.com