ArcGIS Pro’s Layout is designed for publishing with several printing related functionality. The listed page sizes in the insert new layout gallery corresponds to classic printing formats and paper sizes. But today, many of us are producing maps for screen display. After the “ISO – Landscape” section add a new list: “Screen Rations – Nominal Sizes”. In this list, there will be 4:3, 16:9, 16:10, etc. Choose the longer side of this ratio to match the longer side of A/4 or Letter to avoid font size confusions. In this case, the size would be fake, but the result would perfectly fit to the selected screen.