Hi Elainep,
As per the issue description mentioned above, you are facing issue when trying to export, is that correct?
As we have checked the account details using the email address you are logged into the forums, you have subscription for Export PDF.
Try exporting PDF online using a web browser at this link: https://cloud.acrobat.com/exportpdf and check if that works.
Also, try updating Reader using "check for updates" option under Help menu and check if that helps. You may also visit this link to download updates manually: Adobe software and product updates , reboot the machine after installing update and try exporting pdf files again.
Let us know if you need any help.
Shivam