The plugin looks promising, but there are some feature which it need.
1. Send Download option.
In the product page, it must have "send download" option to test, or send it to friends and family for free. Even small plugin like "PayPal File Download" have this option.
2. Additional Download after limit expire
If the client ask for additional download, after the download limit, it should have a option to make the download link alive again. However send download option can solve it other way around.
3. Multiple files download
Another must need feature to sell bundle or album. Zip is not an option for mobile users. In the bundle it needs to have the option to add 2-3 pdf files, and download link will get 2-3 download links in the email too...