Thanks for the advice even though you answered it a few weeks ago although I was asking how to show a center line and now I wanted to show center marks. but Pro/E is not that intuative in creating these unlike in my past job where we used solidworks and creating CL was a snap
Center Lines & Center Marks are one in the same for ProE. At times, you will need to create an axis on the model for features such as slots so they will show a center line in your drawing.
On another note from your previous post, you should be showing your dimensions instead of creating them on your drawings. This way you will keep your parametric relation between your drawing and part plus also make it easier to make modifications later on. I understand it is not always possible, but is good practice. I've attended a few classes and they never pushed this enough.