Best option to add security to a back door?

Hi all,

I'm moving into a rental and the back door, leading to the backyard, only has a latch. The backdoor goes into a mudroom where my main, locked door is, but I will keep outdoor equipment in the mud room. I want to add something better to the door for security and was thinking a deadbolt but I would have to do a lot of work on the door and the frame to add that functionality in. Is there anything else I could add that would be helpful for security, but wouldn't take as much work?