How can I hang a large but light poster on a concrete pillar?
Tape and concrete don't really mix that well.  It might initially hold, but it will eventually let go.

The best solution is to drill a hole and use a light concrete anchor or concrete nail.  Alternatively, you can use a special metal band that wraps the pole and has an attachment on it (sorry, I don't know the exact name of these) - they are often use for street signs like in the below image. 



Image Source: http://isostainless.com