When you try to to upload custom font for PDF export, and the font filesize is bigger than the current attachment size limit, Confluence will refuse to accept it with the following error:
The following error(s) occurred:
- Your request could not be processed because a required security token was not present in the request. You may need to re-submit the form or reload the page
There is nothing logged in the logs. It'd be nice if Confluence can say something more understandable for end users, e.g. "The Font filesize you're trying to attach is bigger than your current attachment size limit. Please increase your attachment size limit then re-upload again."
Increase attachment size limit and re-upload again.