Final answer:
The BeginPrint event of the PrintDocument class is triggered before each PrintPage event, and it is used to prepare resources and settings for a print job in .NET applications.
Step-by-step explanation:
The event of the PrintDocument class that is triggered immediately before each PrintPage event occurs is the BeginPrint event. When you are working with the PrintDocument object in .NET to handle printing, the BeginPrint event is useful for initializing any resources or setting options that are needed for the print job before the actual pages start printing, which is indicated by the PrintPage event triggering for each individual page to be printed. The BeginPrint event is therefore an essential part of the printing process in .NET applications, enabling developers to prepare for the printing tasks ahead.