Solved! Go to Solution.
Your issue could also be browser related, have you tried in another browser?
We have since found the cause: CSS includes used for formatting on the rest of our Sharepoint site were added within the Custom CSS section of the form. Removing there (as per advice of Nintex Support) fixed the problem for the moment.
That's great that it was resolved. And yes, we have seen in some related posts that some JS or CSS can affect how Print to PDF functions. Feel free to mark your answer correct so others can learn from your experience. Thank you for posting back