Why can't I create a PDF of printer spreads from InDesign print booklet?

I'm trying to create a booklet from InDesign, but when I try to select "Save as PDF" from print booklet I get an error that says this is not supported. I'm on a relatively new mac, with the newest version of InDesign CC.

I tried a workaround and saved as a Postscript file, with the idea of opening it in Preview or Acrobat and saving as a PDF from there. When I went to save the Postscript file, the Setup dialog box would not allow me to specify anything:

However, the print booklet preview looked okay, so I went ahead and saved it. It should be a booklet with the spreads trimmed out of an 11x17 page, but when I open it in both Preview and Acrobat, it shrinks to fit an 8.5x11 page. Because I can't specify the size when saving (see screenshot above), I don't know how to change this. The actual size of the InDesign document is the correct size — one spread fits on an 11x17 with crop marks.

Basically, my questions boil down to this:

- How can I save my document as a file with imposed spreads?

- Why is it so difficult to do this fairly common task?

- Why have options to export as PDF from print booklet that simply don't work?

- Why can't I make any specifications when saving as a Postscript file?