i mean a functionality like the mod showed here http://www.nopcommerce.com/p/177/product-specification-value-mod.aspx
And could be great if you have a plugin for upload downloadable information of the product (in a new tab) to download manuals, firmware updates, and so on.
This for v2.6, because is the version that we use.
We are not aware of such a plugin. You can try to contact the creator of this plugin for 1.9 if by any chance it is available for 2.x. By the way you can add custom values for specification attributes in nopCommerce 2.8. You can read more about this in this blog post:
Hope this helps!