If you have a PDF virtual engine, then Print Preview won't export the PDF. You actually have to use the Print function in order to make Adobe Acrobat DC to export your file. The print preview will only show you the content in a window without exporting the file in the PDF form.
If you have issues with Adobe Acrobat DC, then I recommend installing CutePDF Writer. It works on the same principle and just like Adobe Acrobat DC, it allows printing directly to PDF where there is a Print function available.