Can we attach a PDF file and require that volunteers read it when they sign up?

While administering the relevant event, go to the Settings tab | Prompts sub-tab and add a Custom Prompt.  Select the Checkbox type and enter text along the lines of “I have read the volunteer requirements” as the description, check the Hyperlink option beside the description and type a link to your PDF.  The PDF can be on your own website, or you can press Select to upload it from your computer to ivolunteer.com.