Displaying numbers with the right sign I have an odd question: how can I persuade Numbers to show the signs of a series of numbers which may be either positive or negative? The negative sign is a default setting, but there appears to be no default to show the plus sign for positive numbers. It would be useful if it existed, or if some bright spark has a work-around.
At least in older Numbers versions (in my example it's Numbers 3.2.2/Mavericks 10.9.5) you can define a custom data format.

Hit the "Cell" tab and the "Data Format" drop down menu > Create custom Format….

Use the default Number format and apply an additional rule like in the screenshot below:



and hit the OK button. Then apply the custom format Number+ to all appropriate fields.

The custom format is document based. You have to configure it anew for every new document.