Thanks for the reply. I've tried opening them via another document but it doesn't work. I just tried to send you a copy and it says "the file could not be found. Please make sure this is a valid file and try again." This is for both the PDF and word files that have gone a bit weird.
Also I've tried to cut and paste these files and I get the message "accesss is denied. Make sure the disc is not full (it's not) or write-protected and that the file is currently not in use."
Any other ideas?