You can add graticule lines to your map in lat/long, as long as the map has a coordinate system defined for it.  Simply use the Map Tools | Add to Map | Graticule command.

For example:

1. Create a map with a coordinate system.
2. Click Home | New Map | Contour, select Conifer.grd from the Surfer Samples folder and click OK.
3. To verify a coordinate system is specified for the map, select Map in the Contents window, and in the Properties window click the Coordinate System tab. You can see the UTM coordinate system is specified for this map.  If a coordinate system is not specified for your map, click the Change button, select the coordinate system and click OK.
4. Now to add a graticule, click Map Tools | Add to Map | Graticule. The graticule is created over the map and you can see the new Graticule layer in the Contents window.
5. You can select the Graticule layer in the Contents window and in the Properties window change the graticule properties, such as line color, line spacing, label location and label format.

Please see attached SRF file for example.

Updated September 1, 2020