First, you could add a map collar using the Map | Add | Collar command. The map collar labels can be rotated by:

1. Clicking Map | Plot | Plot Properties.
2. On the Collar Ticks page of the Property Manager, in the Outer Ticks section, expand Major Ticks and Labels.
3. Check the Same label orientation checkbox or set the Label angle.

Alternatively, you could export the graticules to a vector file and then recreate the graticules as a base map. To do so:

1. Create a new layer by right clicking in the Object Manager and selecting New Layer. 
2. Click Map | Add | Graticule. 
3. Click Map | Plot | Plot Properties and then set the graticule properties on the Graticule and Graticule Ticks pages in the Property Manager.
4. Turn off all layers except the graticule layer. You can do this in the Object Manager by clicking on the eyeball icon () to the left of the layer name. When the eyeball is gray and has a diagonal line through it (), that layer is turned off.
5. Click File | Export. Type in a File name, such as "graticule", and set the Save as type to GSI - Golden Software Interchange (*.gsi). Click Save.
6. In the first Export Options dialog, leave all of the boxes unchecked and click OK.
7. In the second Export Options dialog, click OK to accept the defaults. 
8. Create a new layer by right clicking in the Object Manager and selecting New Layer.
9. Click Map | Create Map | Base and select the graticule.gsi file. Click OK in the Import Options dialog and the lines and labels are displayed. 
10. Click and drag your mouse on the page to select all of the labels that are vertical.
11. Click Arrange | Rotate | Rotate. Type in the desired value for the Counterclockwise rotation in degrees value. Uncheck the box to Rotate objects about the group pivot point and click OK.  The labels are now rotated.
12. In the Object Manager, click on the empty layer that has the graticule on it.
13. Click Map | Add | Graticule to remove the graticule.
14. Right click on that same layer in the Object Manager and click Delete Layer to remove it from the project.
15. Click the eyeball icons in the Object Manager to turn on all the layers you want to be visible.

If you would like to be able to rotate graticule labels in MapViewer, let us know!

Updated June 8, 2018