Download PDF from Trigger

gistfile1.java

global class PDFDownloader {

	// called from trigger
	@future (callout=true)
	public static void download(String sessionID, String attId) {

		String vfEndpoint = 'https://c.cs10.visual.force.com/apex/PDFTest_mrk?id=' + EncodingUtil.urlEncode(attId, 'UTF-8');
		String vfSessionURL = 'https://cs10.salesforce.com/visualforce/session?url=' + EncodingUtil.urlEncode(vfEndpoint, 'UTF-8');

		Http http = new Http();
		HttpRequest req = new HttpRequest();
		HttpResponse res = null;
		
		// request vf pdf page
		req.setMethod('GET');
		req.setEndpoint(vfSessionURL);
		req.setHeader('Cookie','sid=' + sessionID);
		res = http.send(req);

		// follow 302 redirect
		String vfGetSIDURL = res.getHeader('Location');
		System.debug('vfGetSIDURL=' + vfGetSIDURL);
		req.setEndpoint(vfGetSIDURL);
		res = http.send(req);

		// grab vf session id out of cookie
		String cookieString = res.getHeader('Set-Cookie');
		String vfSID = cookieString.split('sid=')[1].split(';')[0];
		req.setEndpoint(vfEndpoint);
		req.setHeader('Cookie','sid=' + vfSID);
		res = http.send(req);

		// extract pdf from body
		Blob binaryPDF = res.getBodyAsBlob();
	}

}