PDFViewerOptions.FitWindowToPage

From Xojo Documentation

Property (As Boolean )
aPDFViewerOptions.FitWindowToPage = newBooleanValue
or
BooleanValue = aPDFViewerOptions.FitWindowToPage

New in 2021r2

Supported on Mobile.

If true, the window opened in the PDF Viewer application will resize to fit the first page of the PDF document.