Preukaz na VZV is a forklift driver's license (vysokozdvižný vozík). You cannot work on a forklift in a warehouse or factory without it — this is a work safety requirement.
In warehouse job offers, "preukaz" is often written as a "preference": operators with it are paid a higher rate. You can get it through short courses; the validity of the license (only with the employer or everywhere) depends on the type of course — ask for details when you sign up.