{
	"source": [
		{
			"type": "html",
			"data": "<p>Hello world</p>",
			"options": {
				"format": "A4",
				"'printBackground" => true,
				"margin": {
					"top": "5mm",
					"right": "5mm",
					"bottom": "5mm",
					"right": "5mm"
				}
			}
		}
	]
}

“options” parameter is optional, the default value is {“format”: “A4”}
Passing several object to “source” array, you can concatenate different html-converted pdf with different options.