I can save in .pdf just one or two pages at one time, using default Mac viewer. But I have several hundred of pages to save. Does anyone know how to do it faster?
You could try importing the individual pages inside the help files into Calibre and then export as a book format or PDF
Since the .help files are just HTML pages, this could work but I guess the linking might not work correctly
Here's a page from the Calibre features talking about HTML pages import