I've been digging around for a simple solution to including a "download original" link in NextGen image galleries. I've tried a few plugins with varying success, but found this one to work in the easiest to manage way.
I realize this is a pretty specific thing, combining two plugins, but I saw that others were trying to do this without much luck, so I thought it would be worth posting here.
Getting this to work took a few steps.
1. in the nextgen settings, be sure to store your images and galleries in the uploads folder.
2. create your own custom template for the nextgen gallery, and get that operating
3. insert the a download link into that template using do_shortcode to trigger the Download Shortcode plugin. My code looked like this:
<?php echo do_shortcode( "[download label='Download'] $image->imageURL [/download]" ); ?>
I had about 4 galleries set up and displaying in a single album before I tried this approach. It did not seem to work at first, I think because the images were not originally uploaded within the uploads folder. Changing the nextgen preferences to store images and galleries in uploads did NOT correct the issue for OLD galleries. Any NEW galleries that were created after the change all operated correctly with the Force Download call. So, you should either make all the settings changes first, or be prepared to reupload all your old galleries to make the download links work.
Thanks for a useful plugin and informative support section here.