Hi @vivjiang thanks for your question!
Yes, there is a way to download a canvas as a .png, however, downloading as a .pdf is not supported at this time.
To download the canvas, you must group select the canvas and objects contained within, then right-click and select Download. This will download a .png file of your entire canvas.
You can learn more about the download options in a workspace in this topic.
Please let us know if this helps solve the problem 