Exporting Your PDF
Once you're happy with how your contact sheet looks it should be exported to a PDF. When exporting the images will be rendered according to the compression settings and the PDF made available to save. Use File -> Export Contact Sheet…
, or the keyboard shortcut Shift+Cmd+E, to export the PDF.
When the PDF has finished rendering you will be prompted for where to save the file. If you set a title for your contact sheet that will be used as the default filename for the PDF.