1. There are two ways to take notes in Zotero - directly on the PDF or in a separate note. Taking separate notes is especially useful if you are working with a source that doesn't have a PDF (e.g., print books, print reports, artwork). To take these kind of notes in Zotero, first choose the item within your library that you want to add a note to by clicking on it in the center pane.  Next, go to the right-hand pane and click the "notes" icon.

2. Next, click the + button to add a note.

3.  Type in the text editor that opens up.  Your note will be automatically saved as an attachment beneath the item (article, book, etc...) as you are typing.  Note:  you can edit the note in a separate window by clicking on the 3 dots in the upper right corner.  Doing so provides you with more screen flexibility while taking notes.

4. The text editor also has rich text features. This means you can highlight notes, make lists, or use other editing tools to help make your notes as meaningful as possible for you. In this example, I highlighted the key definition so I could easily find it again. I also used a different text color to signal to myself when I am brainstorming my own thoughts vs. taking quotes directly from the text.

5.  You can add multiple notes to an item.  Sometimes it is helpful to see all of the notes in a collection at once. To see all of your notes, place your cursor in the center pane then hold the shift and + keys at the same time.  All of your items will be displayed so you can see the attachments beneath each item.