Hello @ChristinaL555 ,
The issue that's occurring is because of the sheer size of the email trying to be converted to a PDF. When an email gets exceptionally long, it can cause errors with compressing and downloading, which translates to the error when the PDF tries to be created. Sometimes as a workaround, you can:
I can confirm that the workaround I mentioned worked on my end. In the future, it may be in your best interest to use Read More links and other ways to shorten the email, or to make the newsletter itself a separate PDF that can be hosted and linked from elsewhere.