Disorganizing books or resources that are commonly used and require organization to be used effectively.
Disorganizing books and resources can be an ongoing prank, wherein you simply ensure you return any of the resources in the wrong order each time you access them. This serves as a mild irritation on most, and will decrease the productivity of the overall office.
This prank also can be used on a target if they have a shelf or drawer of materials. For those that organize their materials, the chaos will be noticed immediately. For best effect on an individual, only move one book at a time. They may notice the change, but be unable to accuse anyone lest they look crazy.
If more flair is needed, hide one key resource every two weeks. When the next week starts, swap it out with another. Changing the missing resource after this time allows staff members to build a pattern of working without the missing resource. The consistent change in missing resources will be difficult to adapt to in the long run for most staff.