https://learn.microsoft.com/en-us/dotnet/api/system.drawing.printing.printdocument.onbeginprint?view=netframework-4.8.1&viewFallbackFrom=windowsdesktop-10.0
PrintDocument.OnBeginPrint(PrintEventArgs) Method (System.Drawing.Printing) | Microsoft Learn
Raises the BeginPrint event. It is called after the Print() method is called and before the first page of the document prints.
printdocumentmethodsystemdrawingprinting