If you own a LEGAL copy of Adobe Acrobat, or any of the other Adobe Creative Suite 4 applications, and have suddenly received a “Licensing for this product has stopped working” error message, uninstalling and reinstalling is not likely to fix the problem. 
Adobe is apparently aware of the issue, and has posted a KnowledgeBase article covering some possible solutions. The article covers all operating system versions that CS4 will run on, and offers several solutions you can try (in order) to fix the problem.
I have Adobe Acrobat 9 standard installed a few days ago. It was working fine. Now If i open a pdf document document, it give error as ”
Licensing has stopped working contact adobe support”
Please help