Make first sure that you have updated your Adobe Reader
Make sure you have installed the latest version of Adobe Reader (https://get.adobe.com/reader/)
Remember to UPDATE If you are on Mac, the reading of a pdf is by default on the application PREVIEW ==> it is necessary to install the free version of adobe reader for mac
Remember to change “browser” if necessary
Good to know: some phones do not have enough “memory” to display the HD version. Then prefer to download the BD version (low definition)