Hello! If you can't open the PDF then there is likely an issue with your ability to view PDF files. On desktop, you can download a PDF viewer or you can set your browser as the default way to view PDF files. On mobile, some platforms support reading PDFs without a specific app, but some also don't so you have download an app that can view PDFs (Google Drive, an eBook reader, Adobe Reader).
For more options and more detailed help, please see this website: https://www.wikihow.com/Open-PDF-Files