Article to Article (Elsevier)

[Bruce Pourciau]

A document written in Article (Elsevier) class, produces the following  
error message when trying to View PDF (pdflatex):

Package geometry error: You must set \paperwidth properly
Package geometry error: You must set \paperheight properly
\...@process
Set your paper type (e.g., `a4paper' for A4) as a class option
or as a geometry package option.

I have US Letter selected in Document > Page Layout.

I assume this is something very easy, but...

Bruce