Allow to set additional PDF export options

[knoxi]

Extend the configuration options to support additional PDF options when export to pdf, like

• Format
• Landscape
• Scale ...

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[knoxi]

@MaxMelcher This doesn't seems to be done, right?