Using the latest version of boxcryptor, I always get the message "You don’t have permission to save the file " when trying to save a pdf.
I confirmed under info that I have read/write permission on the file and all directories involved.
Please contact us via the support email-address (support@boxcryptor.com) by sending us a debug log:
https://www.boxcryptor.com/en/help/faq-and-troubleshooting/macos/#how-to-create-a-debug-log