You can also add a file (PDF, Word, etc.) to a reference by clicking on its title and then clicking the paperclip icon at the top of the center column. You can then select:
- Attach Link to URI... to add a link to a web page or to a program on your computer
- Attach Stored Copy of File...
- Attach Link to File...
You can also right click on an item's title and then choose Add Attachment to see the attachment options listed above.