Hi Amanda,
Are you able to open other PDF files on the same computer? Are you trying to open in Acrobat or Reader (and what version), and is the file saved locally or to a network drive? Was the PDF saved as an email attachment?
If you'd like, I'd be happy to take a look at the file in question here. Let me know if you'd like to send it, and I'll send a private message with my contact details.
Best,
Sara