Hello Wilhelminav,
We apologize for the inconvenience caused, as per the description above, you are not able to use Adobe ExportPDF service on your Macbook after an OS update and PDF files are not opening, Is that correct?
The record shows that you are subscribed to Adobe ExportPDF service on your current Adobe ID, you can access the service through the URL https://cloud.acrobat.com/exportpdf with your Adobe ID and password on a browser like Chrome, or Firefox, or Safari.
If you are trying to use the service through the freeware Adobe Reader DC and facing the issue, please sign out and sign back in Adobe Reader using your Adobe ID and password, check for any pending updates from help>check for updates. Reboot the machine and try exporting any PDF file.
If you are not able to open PDF files, you can refer to Can't open PDF
For more troubleshooting related to Adobe ExportPDF, please refer to Troubleshooting Create PDF, Export PDF, Adobe Send, Fill & Sign … services(PDFPack or Document Cloud Services).
Feel free to update this discussion for any further assistance.
Regards,
Anand Sri.