This article explains how to convert a Google Doc to PDF. The Google Docs website provides a few ways to do this depending on what you want to do with the PDF after it's been converted.

You can save a Google Doc as a PDF via the File menu in Google Docs. From there, you also have the ability to email it as a PDF attachment. The same tasks can be accomplished via the Google Docs app ...

Export any document in your Drive account as a PDF and sync it back to Drive. Google Drive enables you to export any file to PDF.