In total there are 2 shortcodes you can use:
1. Full catalog Export Shortcode
[pdf_catalog category="full" text="Export Complete Product PDF Catalog"]
2. Specific product category
[pdf_catalog category="CATEGORY_ID" text="Export Product Category X as PDF"]
A Widget is not supported. But you can use the shortcode in a Widget. You only need a plugin, that adds shortcode support for widgets.