I have a document that is letter and my printer has letter paper, but Okular always tries to print it as A4.
I’ve checked both the printers default settings and Okular and it says letter everywhere, but still A4 is sent to the printer.
I’ve googled this and have seen reports that date back to 2009 complaining about QT, in most cases it says that it was fixed in a later version, but in my new Manjaro installation (2 mo old and up to date) it seems to be still this bug.
I’ve checked /etc/paperspecs and I do see letter defined there.
Also if I print a test page the printer doesn´t complain about incorrect paper size. So it seems to be an Okular specific problem.