This section allows you to upload an IMAGE only. NO PDF FILES. Given that your event listing is dynamic and conveys more information than a flyer, we suggest you upload one if you already have the image made. Otherwise, it makes little sense to create one for your online listing.
You can use this section of the site for other purposes if you change the name of the button on your event listing from EVENT FLYER to whatever you want (in the DISPLAY OPTIONS area of the EventBuilder) and upload whatever image you want.