If Booklet, side-fold is not an available
option, the selected paper size may be too small for the pages. Make
sure that the paper size is twice the page size.
Under Preview, you can see how two of the pages will appear when they are printed on one tabloid sheet.
Note Your booklet will print correctly
only when the total number of pages is a multiple of four, but you don't
have to place content on all four of the inserted pages. You can leave
some of them blank.