In the end I worked around this using PDFMerger:http://pdfmerger.codeplex.com/releases/view/37934 to merge a cover and the rest of the file.
As an aside, their api has a really nice format for specifying how to receive the PDF, might be a nice enhancement to PDFCrowd at some future date:
$pdf = new PDFMerger;
$pdf->addPDF('samplepdfs/one.pdf', '1, 3, 4')
//REPLACE 'file' WITH 'browser', 'download', 'string', or 'file' for output options
//You do not need to give a file path for browser, string, or download - just the name.
$client->convertUri("http://some.com/pdf.html", "download", "file.pdf");
very intuitive and quick for developers.