It is correct that the "necessary" in bold in the following sentence.
If it is skills' adjective, I wonder why it isn't placed before the word of skills? If the "necessary" be placed before "skills", will the object of the infinitive phrase change? - "to make successful scientific presentations"?
Sentence:
The main purpose of the seminar is to provide students with the opportunity to develop the confidence and skills necessary to make successful scientific presentations.