You can test this with the Qt own example fontsampler (http://doc.qt.io/qt-5/qtwidgets-painting-fontsampler-example.html). Regardless what you configure it ALWAYS printers on US-Letter Portrait - for PDF and pysical printer.

I thik this relates to the following change: http://code.qt.io/cgit/qt/qtbase.git/commit/src/printsupport/kernel/qprinter.cpp?id=21e5da2fe0a3c9450de60b846d2f0836e4455976

The PDF was generated selecting A4 with Landscape (the content is landscaped but the page it self is not): https://up.frubar.net/3917/print.pdf

This was not the case for Qt 5.11.

OS: Linux (Arch Linux) qt5-base Version : 5.12.0-3