You can find the "Print" option from the bottom menu by swiping it up. Please see the attached gif. 

You can also move the "Print" or any other function by dragging it to the top row where (Move to delete, Reply, etc) are located.

When using "Two panel UI". From within your message, tap on the Menu -> Copy/Send/Share/Print > Select Send/Share/Print message text. Then choose your printing app from the app selection window. This method allows you to copy the text of the message without formatting. Please see the attached gif.

Choose Google Cloud Print instead to print the message with formatting.