Upload the whole plugin folder to your /wp-content/plugins/ folder.
Set write permission (777) to the plugin dir folders => wp-mpdf/cache AND wp-mpdf/mdpf/graph_cache AND wp-mpdf/mdpf/ttfontdata
Go to the plugins page and activate the plugin.
Add to your template "<?php if(function_exists('mpdf_pdfbutton')) mpdf_pdfbutton(); ?>" as a small button or "<?php if(function_exists('mpdf_pdfbutton')) mpdf_pdfbutton('my link', 'my login text'); ?>" as a textlink. The second text specifies the text which should displayed if you have checked "needs login" and a user isn't loggend in.
(if you wish to open the pdf print in a new tab you may pass "true" for the first parameter)
You can adjust some options: in your admin interface, click on plugins and then on wp-mpdf. For allowing or disabling pdf export you can use the checkbox when creating/editing a post or a page.
Place your templates into /wp-content/wp-mpdf-themes
Requires: 2.8 or higher Compatible up to: 3.3.1 Last Updated: 2012-2-3
Downloads: 10,199