Double click on either axis to enter Axis Options where you can change the font. Double click the legend to open Chart Legend Options where you can do the same for plot legend. These windows are also available via Options -> XY Options.
Do you have any idea as to why the default font size 12 appears to be so small? Is there a way to permanently override that? Setting the font size to 48 makes it legible for my monitor Or, is there a function to change it so that is visible at font size 12?
When I select a node the coordinates displayed are illegible.
It seems more like an issue related to screen resolution or other system display settings than to Abaqus itself. Normally it shouldn’t look like that - default font settings in Abaqus are correct in most cases.