Web2Print is a framework to create HTML5 content out of different sources.The extension displays the content in a preview environment which resembles the single rendered pages in the finished document.Since rendering  especially for print production  is a time consuming task, the preview provides the user with the possibility to check the result.
The rendering process itself is finished by the w2pservice, a server- side ensemble of different tools and proprietary code taking care of converting existing RGB Images to CMYK colorspace if needed and creating a print-ready PDF-X3 document.