Take a PDF apart. Save every page as its own file, pull out only the pages you need, or cut the document into several parts using page ranges.
Use commas and dashes: 1-3, 5, 8- means pages 1 to 3, page 5, and page 8 to the end.
Yes. Choose Extract pages and type the page number.
No. Your original stays as it is and new files are created.