If you import a reference that has a PDF attached to it, such as a research article, Zotero will usually download it for you when you import the reference. All references with attachments have a drop-down menu where you can find them again.

You can also add attachments to existing references in Zotero. Right-click on the reference and select Add Attachment and Attach Stored Copy of File.

Zotero can also help you if you have a PDF stored on your computer and want to create a reference based on it. Drag the PDF into Zotero. If the PDF is based on a text file, Zotero can search for metadata (title, author and other necessary information) and create a reference.

NB! Remember to always check the reference after you have done this, it is not certain that all the required fields have been entered, and most often some of the information has been entered incorrectly in relation to APA 7th.

Video: Drag a PDF into Zotero

Video that shows how you drag a PDF into Zotero, so that Zotero can find metadata.

If the PDF is an image or an old document, e.g. something you have scanned, this is not possible. You can still drag the PDF into Zotero, but all necessary information has to be added manually. You do this by right-clicking on the PDF [Mac: Press down with two finger on the trackpad] and choose "Create Parent Item". Then you will see the fields on the right hand side of the screen, where you can fill in all information needed.

Video: Drag a PDF into Zotero and add necessary information

Read more about this on Zotero's help pages.