Does Pathfinder’S Multiclassing Spell Stack?

Multiclassing allows players to gain a +3 bonus to any skills that were previously not a class skill. However, these bonuses do not stack with each other since they are the same bonus. For example, if a spellcasting multiclass character gains Orisons from two different lists, they only get the full complement for their class level in each class.

Some abilities explicitly stack, such as the animal companion levels of Druid and Ranger or the unarmed damage of Brawler and Monk. Some abilities have means of stacking. Multiclass archetypes aim to make the downsides of multiclassing less painful by fitting a character to a concept without making that character. Spells that provide bonuses or penalties on attack rolls, damage rolls, saving throws, and other attributes usually do not stack with themselves.

If you have two different classes, you get the bonus spells for each class and get to cast spells chosen separately for each class. Your attack bonus and saving throws will stack. If you get abilities from each class, they will stack (this is why most people muticlass).

Nature casters (Rangers and Druids) stack their caster levels, and all of their spell slots are combined directly. Multiclass spellcasters do not stack with spellcasting abilities, but combat-oriented classes work.

Multiclassing full casters and Artificers together, and your slots combine in full while your spells known are. You can take multiple spell specializations, but they cannot stack with themselves unless they specifically state that they do or provide multiple separate effects.