Printers sometimes print the pages in reverse order, because this lets them print the pages face up and still have the pages in the correct order. If you look in the printer driver, there may be an option for face down or face up output.
Many people prefer face down output, especially on personal printers, because people walking by can't see what is being printed. On a shared printer, it can make it harder to find your job. People have to turn over the sheets and riffle through them to find their job.