Hi Doris,
Welcome to the E-Learning Heroes community! We're glad you're here. 😀
If only two of the many PDF files cannot be opened, the behavior you're seeing is indeed strange. I appreciate the troubleshooting you've already tried. When you upload the affected PDF files in a new Rise course, will the users be able to open them?
If the issue persists, could I have you connect with us in a case so we can determine what's happening? Our support team might request a copy of the PDF files and the Rise course, which you can share privately via the support case. We'll reach out soon after we hear from you.
