Borrow an Arcane Spell
Source Player Core pg. 193
Skill
Arcana
If you're an arcane spellcaster who prepares spells, you can attempt to prepare a spell from someone else's arcane spellbook or the like. The GM sets the DC for the check based on the spell's rank and rarity; it's typically a bit easier than Learning the Spell.
SuccessYou prepare the borrowed spell as part of your normal spell preparation.
FailureYou fail to prepare the spell, but the spell slot remains available for you to prepare a different spell. You can't try to borrow this spell again until the next time you prepare spells.