Sweep a helical surface (section will be a straight line segment) using the axis of symmetry of your existing geometry. Intersect this surface with the outer surface of the geometry yielding a curve (spiral wrapping the entire outer surface). Create a datum point on the resulting curve and pattern it as required for placement of the holes. Create the first hole using the pattern leader (point) then you can use a reference pattern to add the remaining holes.
You may consider using dimensional pattern as shown below:
In this case the holes are always normal to sitting surface. Hope this is helpful to you.
To clarify your point about the holes being normal to the surface, the method in my first post places the hole using an axis that is normal to the surface of the cylinder. This can be observed in the second picture if you make it larger that axis 5 is normal to the outer surface and DTM 4 is normal to the axis. This same approach can be applied to any surface topology where Creo is capable of generating the surface normal.
This end view of the solid makes this much clearer. All axes on the spiral curve are normal to the outer surface of the solid body.
