This extension provides a "Print Invoice" button on the Admin Orders view screen which generates a PDF of the order details.
Install the prawn_hander plugin
script/plugin install git://github.com/Roman2K/prawn-handler.git
Install this extension
script/extension install git://github.com/bernsno/spree-print-invoice.git
Make sure you have the required gems
sudo gem install prawn --version="0.8.4"
Optional: Set the logo path preference to include your store / company logo (in your seeds.rb / site extension).
Spree::PrintInvoice::Config.set(:print_invoice_logo_path => "/path/to/public/images/company-logo.png")