Will custom fonts for seal cutting involve infringement?

It's infringement.

Article 12 of the Copyright Law of People's Republic of China (PRC) * * * The copyright of a work produced by adapting, translating, annotating and arranging an existing work shall be enjoyed by the person who adapted, translated, annotated and arranged it, but the exercise of copyright shall not infringe the copyright of the original work.

Article 24. Anyone who uses another person's work shall sign a license contract with the copyright owner.

Article 28 Publishers, performers, producers of audio and video recordings, radio stations and television stations, etc. The use of another person's work in accordance with the relevant provisions of this law shall not infringe upon the author's right of signature, modification, protection of the integrity of the work and remuneration.