Very similar to Miro, you can share the board with students via link, upload pdfs from your computer, upload pdfs via url, write on the board, export the board. Etc.

Where it falls short:

On the free version, you can only upload the first page of any pdf. So if you have a pdf of a 3 page worksheet, only page 1 will be able to be uploaded and written on virtually. Additionally, there does not seem to be a clean way to upload Google Drive materials like slides, docs, etc.

However, if you are in a pinch and need a virtual whiteboard just to write on one pdf, or just to write in general - this does that!