When creating a PDF report of a dashboard, there are two layout modes: Optimize PDF for printing and Preserve existing layout in PDF

Optimize PDF for printingedit

This will create a print friendly PDF with multiple A4 portrait pages, with 2 visualizations per page. This is the layout mode that was always used prior to Kibana 6.1, and will create PDFs similar to the following:

Preserve existing layout in PDFedit

This will create a PDF preserving the existing layout and size of the Visualization or Dashboard, and will create PDFs similar to the following:

When creating a PNG or a PDF report of a visualization, the "Optimize for printing" option will automatically be used.