These are global standards aggregators. If your company has a corporate subscription to a standards database (like Techstreet or NORMAPME), you can typically download the DIN 5480 PDF for no additional fee.
If you need the standard for professional engineering work, you must obtain it legitimately. Here are the official vendors: Din 5480 Pdf
Electric power steering columns often use small-module (1 or 1.25) DIN 5480 splines to connect the steering wheel to the column shaft. These are global standards aggregators