Create background pattern with dots

I need to create a print design with a dotted background.

The former layout has been squared, which I could easily define by using a background pattern. User defined patterns do only allow lines and no dots, therefore I am stuck.

What would be best practice to create such a pattern?

The bitmap feature lets me “paint” something dottish, but I lack the option to specify the size of the dot and the distance between the dots.