Publisher ExportAsFixedFormat ignores “Publication Page” while manual PDF/XPS export works

I am migrating a large archive of Microsoft Publisher files to PDF before Publisher is retired.

We have isolated a repeatable problem in older publications.

Example publication:

Publisher page size: 210 x 148 mm, landscape

• Manual export through File → Export → Create PDF/XPS → Options → Print Options
• Settings shown by Publisher:
• One page per sheet
• Paper size: Publication Page
• 210 x 148 mm
• Landscape
• Resulting PDF: 210 x 148 mm — correct

However, both PowerShell/COM and VBA using Document.ExportAsFixedFormat produce a 215.9 x 279.4 mm portrait PDF.

Explicitly using:

PrintStyle:=pbPrintStyleOnePagePerSheet

does not fix the problem.

We tested the same publication using:

Application.CommandBars.ExecuteMso "FileSaveAsPdfOrXps"

This opens Publisher’s own PDF/XPS dialog. The dialog still shows Publication Page, 210 x 148 mm, landscape, and when published through that UI the resulting PDF is correct.

We analysed 349 Publisher files:

•120 exported with the correct page size
• 229 exported with the wrong page size
• all 229 failing files opened with an Adobe PDF / A4 portrait printer context

The Publisher PageSetup.PageWidth and PageHeight values themselves remain correct.

Question:

Is there any documented or undocumented Publisher VBA/COM property, parameter, registry setting, or command that corresponds specifically to the PDF/XPS Print Options setting “Paper size: Publication Page”?

In other words, how can ExportAsFixedFormat be made to reproduce exactly the same page-size behaviour as Publisher’s interactive PDF/XPS dialog?

If this is not exposed through the Publisher object model, is automating the built-in FileSaveAsPdfOrXps command the only reliable approach?

Publisher: Microsoft 365 desktop version on Windows.