Wrong paper size

When my wife creates a PDF, it creates A3 portrait, even if A4 portrait is wanted. It makes no difference what program (Word, Publisher, Notepad etc) is used. The image is positioned in the bottom left corner of the A3.

I can only find one setting for the paper size, in the advanced PDFCreator options. It iften reverts automatically to Letter. It appears to make no difference whether the value is Letter, A4, A3 or anything else.

How to set the paper size?