In Jainism, the best and most pure “mantra for knowledge” is actually the Navkār (Namokār) Mantra, because it bows to those who have perfect right knowledge (samyak jñān) and inspires the same in us.

You can use this as your main mantra:

Original (Prakrit): णमो अरिहंताणं। णमो सिद्धाणं। णमो आयरियाणं। णमो उवज्झायाणं। णमो लोए सव्वसाहूणं॥

Simple meaning (arth):

• Namo Arihantāṇam – I bow to the Arihants, who have destroyed inner passions and attained keval‑jñān (perfect knowledge).
• Namo Siddhāṇam – I bow to the Siddhas, fully liberated souls, forever in pure knowledge and bliss.
• Namo Āyariyāṇam – I bow to the Āchāryas, the heads of the Jain order who teach right faith, right knowledge and right conduct.
• Namo Uvajjhāyāṇam – I bow to the Upādhyāyas, teachers of scriptures and knowledge.
• Namo Loe Savva Sāhūṇam – I bow to all sādhus and sādhvīs who are walking the path of true knowledge and conduct.

Why this is a mantra for knowledge:

• It connects you with the Pancha‑Parameṣṭhi, who are the perfect examples of right knowledge.
• By remembering and bowing to them, we slowly remove ignorance (mithyātva) and strengthen samyak darśan and samyak jñān.
• Both Digambar and Śvetāmbara accept this mantra; only minor pronunciation differences exist, not in meaning.

How to use it for knowledge:

• Sit calmly, recite Navkār Mantra slowly at least 9 or 27 times.
• After reciting, keep a few moments of silence and pray from the heart:

“May my wrong beliefs and ignorance go away, may I get right knowledge like the Arihants and Siddhas.”

You can read more about Navkar Mantra and its meaning here and here