As a teen i would love to take "goodies" such as money or other stuff and hide them. Not because i was planning something dastardly, just because i felt cool. This is simple and really only works if you have a printer that's yours and no one else uses.
Things you need:
-Masking tape (or any tape but masking works the best)
Step 1: Step One:
Apply the tape to the top of your folded goodies, I used a five dollar bill
...Because that's worth hiding...
Then tape that to the inside of the tab that covers the ink cartridges
Step 2: Step 2: (not Even Really a Step)
Close up the door.
Leave it until you need whatever you put in there
Or if you forget and have to change the Ink cartridges!