I use an app called Print n Share, lets you print directly to any wifi printer and from any app, no need to have an airprint printer! It also lets you convert files to PDF on your iPad - you will love it.
After the latest update on canon easy photo print u can now print anything. Just do the screen capture(press home and power). This puts it in your photos. Then just open the canon app and print. Works good so far. I just printed invoice of an order. Hth . This is on my Canon MP560.