If you cannot open the free lessons pages, or any of the pdf pages, the first thing to make sure of is that you have downloaded the latest version of Adobe Acrobat Reader:

http://www.adobe.com/products/reader/

If you already have it and it’s not working, you might need to either reinstall it, or upgrade it to the most
current.

That is about all we can do on our end to help troubleshoot pdf problems. Doing a search online might help you find a solution if these solutions are not working for you.