Metadata is data that describes an item. For example, author, title, journal title, date, and the DOI or URL, are common pieces of metadata needed to create a citation.
The quality of the resulting citation depends on the accuracy and completeness of the metadata provided by the source. Zotero does not create or correct the metadata. You are responsible for verifying the metadata. Garbage in, garbage out.
It's good practice to verify the metadata for each item at the time you add it to your library. This practice will also help you become familiar with your citation style so that when you cite in your paper, the process of creating a complete and well-formatted citation will be easier.
You can't create a citation from a stand-alone PDF with no metadata. The item needs to have the Info Tab with metadata in it for citing.
Add a style:
Remove a style:
You're only going to be using one citation style, so removing styles you aren't using will save you time.
Preview the citation in Zotero for accuracy, and fix formatting before citing in Word.