Marianne, you can open it in Photoshop Elements 6, I imagine you can do it in Photoshop as well.
First save the calendar you created as a pdf. Then go to PSE & open the file. It brings up a choice of which of the months you want to open.
Click on the month you want & open. It will then open that page up for you in a state that you can edit it (it's usually called layer 1).
Do what you wan twith that month & then when you go to save it you go File, Save As & you can choose whether you want to save it as a .psd or a .jpg
I hope that helps you.