Envira Gallery Downloads addon allows you to add a download button to to your WordPress image galleries.
You have the option to enable or disable the downloads feature on each gallery, choose a download button position, as well as have the option to display the image download button inside the lightbox view. Our WordPress image gallery download feature also allows you to password protect your downloads.
This requires the visitor to enter the password when they attempt to download an image or the gallery. We took the pain out of creating WordPress galleries and made it easy.