Metadata is information 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 of the source. Zotero does not create or correct the metadata. You are responsible for verifying the metadata. Garbage in, garbage out.
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.
Examples with metadata. Can be used to cite.
Right click > Retrieve Metadata for PDF or
Right click > Create Parent Item > Add metadata
Check against the examples given in the Citation Guide. Examples:
We highly recommend installing the ZoteroPreview plugin. It allows you to preview your citations in Zotero with one click.
But if you don't want to install the plugin, you can follow the multiple steps below.