When you send your docs to trash, you still have a second chance to either restore it or delete it permanently.
Just head to the Trash on the bottom right, and click on your docs' three dots to view the options.
Who can delete docs?
If you're a "Reader" in a channel, you will not be able to trash or delete any docs or collections from that channel.
If you're a "Writer" in a channel, you will be able to trash docs in that channel but not delete them permanently unless you're the doc's author.
If you're an "Admin" of a channel, you have the right to trash and delete docs of that channel.