@amypierce we are supporting PDF links now. Just choose "Link" and paste a PDF URL and we detect it and show the PDF in place of the image.
Also, did you manage to embed Listly in Google Classroom? We are very interested in making sure you are able to do that. For example, this is the code you'd use to embed your list in Google Classroom page:
<iframe src='https://list.ly/list/1f5g/framed?embed_type=iframe&layout=full&per_page=25' seamless width=700 height=2500 style='border:none' scrolling=''/>
You can of course customize the layout and get your own embed code as well from your list page.