Not sure, but I will take clues from the sentence provided.
Professionals should maintain a
high tone by
making new publications available on a rack or table
This tells me that "making new publications" available is a way for professionals to portray this "high tone" to a certain audience (students, public?)
So I would say, a "high tone" is a "good first impression", or "best way to get attention". Professionals would want to maintain that attention or impression.
It would help if you gave the context of this sentence!!
Is it a marketing or sales term?