Example page: http://confluence.atlassian.com/display/ATLAS/Dragons+Stage+2+-+Install+JIRA

Export to PDF, and you will see a blank page for the panel macro in the generated PDF file. See the attached file.

The content is coming from an include macro on the page, with the source page: https://confluence.atlassian.com/display/ATLAS/_Dragons+Hook+JIRA+Up+to+Crowd

Export that page to PDF, and you do not see the empty page in the generated file. See the attached file.

The problem seems to occur when the actual content of the panel runs over more than one page - I could not reproduce this with shorter content.