The issue has been addressed as of 3PM EST and pdf attachments are again being processed without an issue.
Update 07/25/2023 18:06 PM 2 days
ExchangeDefender Encryption is not properly processing .pdf attachments at this time. We are working on a solution now.
If you need to securely send pdf attachments in the meantime please rely on our ExchangeDefender WebShare https://webshare.exchangedefender.com/ service which will enable you to email password protected .pdf files in the meantime while maintaining encryption (and additional password + access control).