If you have a PDF product that will not open at all, or is giving an Adobe error, then you may have received a corrupt download. Please check the file size and verify that it matches with the product description. If the file is too small, you may want to try downloading again just to be sure you have a working file.
If that doesn't help, you may just need to upgrade your Adobe Reader. If you have any version older than 10.0, I suggest you uninstall any older versions and download the newest version. You can get the newest version here - Adobe Reader Download http://www.adobe.com/products/acrobat/readstep2.html. Uninstalling any older versions and installing the newest version should allow you to open the file.
If that doesn't work please let us know your order number and the title of the product that you are having problems with and we can investigate further.