You may need to delete your browsing history or delete some of the pdf files to make room. It would depend on the size that your tablet can hold. Your best bet is to call in and have someone in Student Care go through the steps to do this or you can find the documents here on the community at
http://community.pennfoster.edu/community/academic-help/technical-solutions/content?filterID=contentstatus[published]~category[adobe-reader-pdf-issues There are documents there that can help you. Calling Student Care will give you a person to walk you through the steps. We do not provide support for outside devices and usually only provide support for computers but as long as you can delete your browsing history you should be able to get your pdf files to open again. Once you have done this, we recommend that you do this on a regular basis.
Congratulations on your last exam grade of 80. Great work!