Custom PDF generator

We'd like to build into our website a custom PDF generator, where users can design their own christmas wrapping paper. They can select the type and background colour, a graphic and type in their own words (15 character limit). The design then tiles across the PDF page. Ideally we'd like a live preview of their pdf. And the ability to share across facebook and twitter. You can view the site it will sit on here: [login to view URL] And below is the design of the PDF generator section.