I'm actively looking for a software which lets me read, highlight/annotate PDF files online (web-based) and also do the same on iPad using a software. Additionally, a Windows application which lets me extract the highlights from the PDF file.
I've tried Mendeley, unfortunately the drawback is it's not possible to extract the highlights, and other PDF readers, like Acrobat, Phantom, etc. do not recognise the highlights. Obviously because Mendeley uses a different standard. With Adobe products, it's impossible to highlight online.