No, it doesn’t support carousel and it is not open source. The botfront widget supports Carousels.
For saving PDF’s, you should not pass the PDF itself through Rasa and the tracker store. Instead, your widget should push the PDF somewhere (s3 bucket or something like that) and pass on the URL location or an id for the PDF via the utterance. The PDF url/id would go into a slot that your custom action can use to do whatever it needs to do with the PDF.