As a paying customer we have access to the confluence sources. However we could not find the sources for the PDF export engine (version 4.1.3 key: com.atlassian.confluence.extra.flyingpdf).
As I understand it, the conversion of confluence pages to PDF takes 2 steps:
- convert the confluence page to an intermediate HTML
- export the HTML to PDF using flyingsaucer
The source for flyingsaucer is available but we would be interested in the sources for the first part. Any hint would be welcome!