I have split off your problem from this topic: Change Paper Size - #2 by musa
Bumping a topic that is 8 years old is called necroposting. That is frowned upon.
As far as your paper size problem:
- the library InvoicePlane is using is called mpdf
Try their standard solutions first.
I’m sure there is a mpdf_helper where you can set those things.
The 8 year old solution of applying css might work, but then you’ll have to deal with your footer being only partly shown as you mentioned, which means more css.