title: Merge pdfs with NReco PdfGenerator
body: <p>In the features section on NReco's site, in the examples list: there is a line about MergePdf.
  I have looked in the API-reference and using the intellisense in visualstudio but I can't find anything. </p>
  
  <p>I wan't to merge several pdf's before I sent them in a mail. The Pdf's is generated with nreco wkhtmltopdf with different headers and footers which I could not get to work in the same generate so I splitted the generation and now I want to merge the pdf's again.
  Or do I have to get yet another library involved.</p>