The only way I can think of is to use an image editing application that displays rulers at top and side and can draw lines of any width you determine. Photshop Elements for Mac can do what you want. Other potential editors are
Some Image Editors That Support layers:
Pixelmator - $60
Seashore - Free
GIMP for Mac - Free
Xee 2.1 - free
Most have a demo version that you can test before you purchase.
Pages can add lines at 1 inch intervals but it only has a ruler at the top.