A friend advised me on a pdf viewer with extended commenting capabilities, a bit like the original Adobe solution, but for free:
http://www.tracker-software.com/product/pdf-xchange-viewer
This company also offers non-free pro features, last time I checked single license was 74 $ which is an excellent price compared to Adobe Solutions (more than 800$), honestly it may not be a fair comparison since I did not check if both solution are comparable in term of features and capabilities.
