Apologies if the solution to this problem is obvious to many of you, but I'm a computer dinosaur.
I opened an email attachment (which I'll call document A) from a company I trust, printed it, and saved the email and its attachment in an email folder. Since then whenever I try to open any other.pdf attachments to other emails, document A opens. If I scan and save documents, letters etc, irrespective of what I've scanned, it's still doc A that is saved in my Documents folder. This is driving me nuts. Can someone suggest a solution.