In addition to the font setting adjustments available in PAF 5 Tools-Preferences, at least two other Windows features can have an affect on font size. One is Window size. Are you running PAF 5 in a minimized window? If so, it is possible to 'stretch' or 'shrink' the display width and height by grabbing the side and top 'handles' with the mouse.
Also, a global change in Windows Font sizes can be made in My Computer-Control Panel - Display. But if your Display is O.K. with PAF 4, you probably will not want to change that for PAF 5.