The bug report here mentions that Confluence PDF exports does not handle page layouts. Please include this as a note in the corresponding documentation: https://confluence.atlassian.com/display/DOC/Exporting+Confluence+Pages+and+Spaces+to+PDF.
The note should say something like:
PDF exports will not handle page layouts. This means if you have a two- or three-column layout, the PDF export will still contain the page contents in one single column. The issue is tracked here: https://jira.atlassian.com/browse/CONF-25240