First off, this tutorial is only effective if you are looking to make a quick and dirty single pixel dotted border. If you need a scaleable dotted border this technique will not work well.
Start out by creating a vector shape. You can create any shape that you like but rectangular shapes work best.
Keep your shape selected and take a look at the Properties Inspector. Change the Fill Category to NONE and change the Stroke Category color to anything.
Your image should look similar to my example below.
With your shape still selected, take a look at the Properties Inspector again and modify the Stroke Category options so that they are exactly like my screen shot to the left. Exact options follow:
- Tip Size = 1
- Stroke Category = 1-Pixel Hard
- Edge = 0
- Texture Name= Grid 3
- Amount of Texture = 100%
De-select your shape and your image should look like my example below.