Create additional PDF in Magento

Magento 1.5.1 Community Editon. Our customer wants an extra button in the magento backend under: sales/shipments - specific shippment. In the shipment detail screen there should be a new button "create cover letter" next to "back", "print", "send tracking information". By hitting this button following action has to be done: One PDF with 2 pages should be generated for print out. First page: this page should be a cover letter with the name of the customer taken out of the order and some static text. The second site of the pdf should be a return shipments label with following data taken out of the order: - date of the order - name of customer - invoice number - cutomer number - the order details: sku, product name, quantitiy in a table: please take look at the attachment and again with some static text. We will provide the layout of the document and the static text.