There's an easier way for Photoshop.

1. Select a common brush tool. Pick a diameter you want (I used 3px).
2. Open brush settings. Use none but Dual Brush.
3. By modifying Spacing and Diameter of Dual Brush settings you can get an evenly dotted line with various sizes of dots and spacing. Experiment!

Click image for larger version. 

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And no need to install anything! All the dotted lines here were drawn in Photoshop.