PDF Button doesn't show
Make sure your site pro license is activated on your site. If it is please contact support.
This is caused by the PDF service not being able to access your estimate or invoice. Commonly this is caused by the status of the estimate/invoice being set to "Temp" which is a status that prevents clients (or anyone not logged in) from viewing. To solve this you will only need to update the status of your estimate/invoice.
Generated PDF needs to be updated
Refreshing the cached PDF is simple: just save the estimate or invoice within the admin and the cached PDF will be deleted.