How do I save as a pdf?

You can shortcut (⌘+P) to open the Print panel, click the PDF button, and from that sub-menu, choose Save as PDF. Note that this will give you a PDF name with .pages (e.g. foo.pages.pdf), and you can change that accordingly.

Pages also supports File menu > Export To > and PDF…, where you can select the quality (e.g. Best), and a save location. This approach does not cram .pages into the filename.

You are welcome.