global class QuotePDFGenerator {
  webservice static String AttachPDFToQuote(string Id) {

      try {
        String quoteURL = '/quote/quoteTemplateDataViewer.apexp?headerHeight=156&footerHeight=94&summlid=0EH800000000fkT&id=' + Id;
        PageReference page = new PageReference(quoteURL);

        // Blob loadedPage = page.getContent
        // When using this method, I get "Error, Failed to load PDF document." when trying to view the PDF

        // When using `getContentAsPDF` I get a blank PDF.
        Blob renderedPDF = page.getContentAsPDF();

        QuoteDocument doc = new QuoteDocument(QuoteId = Id, Document = renderedPDF);
        INSERT doc;

        String Name = [ SELECT Name FROM QuoteDocument WHERE QuoteId =: Id ORDER BY CreatedDate DESC LIMIT 1 ].Name;

        return Name;
      } catch(exception ex) {
        System.debug('Error: ' + ex);
        return ex.getMessage();
      }

  }
}