using pro 2.7.3 on a win10 box (10.0.19041.928)
I made a layout with page setup in ISO_A1, simple mapframe, scale bar, two text boxes. Export to pdf works fine (left)
After I change the page setup to ISO_A2 the layout looks the same on my screen but after I export to pdf that pdf has only part of the layout. (right)
I would have expected the extent in the pdf to be the same as in the layout. Is this a bug? or what am I missing? It is repeatable.

thanks for your time
Bert