In pathfinder magic an arcane spellcaster can memorize a lower level spell into a higher level spell slot if they wish.
Eg use a 3rd level spell slot to memorise a 2nd level spell.
Does this include cantrips?
Arcane Spells Wizards, sorcerers, and bards cast arcane spells. Compared to divine spells, arcane spells are more likely to produce dramatic results.
Spell Slots: The various character class tables show how many spells of each level a character can cast per day. These openings for daily spells are called spell slots. A spellcaster always has the option to fill a higher-level spell slot with a lower-level spell. A spellcaster who lacks a high enough ability score to cast spells that would otherwise be his due still gets the slots but must fill them with spells of lower levels.