How can I make a PDF/A of my document that measures 47,4 x 33,3 cm

I am trying to make a PDF/A for a large size document. I open PDF Creator and drag and drop the Word document into the editing window. However, the pane then only shows part of the document. It looks like a A4 cut-out. I have set the hardware settings the PDF24 printer to PostScripts Custom Page Size under Printing Preferences and Printing Defaults under Properties/Advanced and rebooted the computer, but this makes no difference. Can you please help?

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