There are 3 page layouts :

"Single sided" : in this case Tidy It Up ! prints all pages in the normal way.

"Double sided/p. 1,3,…" : in this case, Tidy It Up ! prints odd pages starting from 1, 3, 5, ….  When the printing of this half is done, you should reverse the printed pages to start the second print job to print the even pages using the "Double sided/p. 2,4,…" option.  You should take care that Tidy It Up ! prints the pages starting from 2,… ; the way you put back the pages depends on your printer paper tray.

"2 Cols/p. 1,3,…" : in this case, Tidy It Up ! prints odd pages starting from 1, 3, 5, …. in a double sided form, but in two columns, this means that you can make a nice little book by folding the pages.  When the printing of this half is done, you should reverse the printed pages to start the second print job to print the even pages using the "2 Cols/p. 2,4,…" option.  You should take care that Tidy It Up ! prints the pages starting from 2,… ; the way you put back the pages depends on your printer paper tray.  Don't forget to select the landscape orientation if you want it !