From the introduction:
Savage Worlds and the various Companions and Settings provide a range of different Arcane Backgrounds, most of which can be extended or customised through trappings to cover a range of different arcane concepts.
However it’s not uncommon for GMs to design or heavily customise their own Arcane Backgrounds, particularly if they’re basing the magic in their campaign on specific mechanics from other games, novels, or movies.
Savage Arcanum simplifies the creation process and makes it easier to balance new Arcane Backgrounds by breaking down the various options into a series of arcane abilities, in the same way as Savage Armoury and the race creation rules.
This document is intended for GMs who are designing new Arcane Backgrounds for their own settings. Like the race creation rules, Savage Arcanum can be highly vulnerable to min-maxing if players are permitted to design their own Arcane Backgrounds.