Giving edit access to Google Drive documents is sufficient. The way these files work, once they are shared with a user, the file will appear in their "Shared with me" list
If they remove or delete a file from this list, it will not remove the document from any other user's list, nor will it destroy the file. Only the owner can trash a document.
Learn more about trashing documents here: http://support.google.com/drive/bin/answer.py?hl=en&answer=2494934&p=restore_trash_collab
If the owner trashes a document, they can get it back from their Trash folder:
Learn how to recover a file or folder that you moved to the trash.
If something in Google Drive is moved to the trash, you'll see a
warning and you may lose access to it at any time. Read one of the
following sections to learn how to restore it to your Google Drive
from the trash. When you restore something, it'll be recovered in
Google Drive on the web, to the Google Drive folder on your computer,
and to your mobile devices.
If the item is in a folder, you’ll need to restore the entire folder
to recover any individual items inside of it.
Owners
If you're the owner of something and you’ve placed it in the trash,
you'll see a warning that reads "This item is in your trash" when you
open the doc or file.
If you’d like to restore a doc or file to your Google Drive:
Search for it in the Trash. Select the file(s) or doc(s) you’d like to
recover. Click the Restore button.
Folders and file structures behave the same way, if regular editors remove these it will disappear from their "Shared with me" list but it only affects them, not the rest of the collaborators.
Google Drive does not offer the option to search for other users' public documents (see here).
However, it is possible for users to find these documents via Google Search using a filter. In order to search exclusively for public Google documents, a user would have to search using the following:
site:docs.google.com/document/d [keyword]
To create a tool that would allow users to search for these documents, you might consider simply creating an HTML form that submits to google with the site:docs.google.com/document/d prepended.
Here's a quick demo of that using AngularJS:
https://github.com/cweems/Google-Docs-Search/tree/cc00038e67d6d3ff15ae19a271f0bfec99437b41
Navigate to the 'app' folder and then open index.html in your browser. Enter keywords into the text box and click submit: it will return a list of results that are only Google Docs.
Best Answer
You could use "Publish to the Web" (File > Publish to the web). It generates a page with the documents content and cryptic link. Visitors can only view the content. Here is an example: https://docs.google.com/spreadsheet/pub?key=0AvxYoiW50CjLdC1QRDh5eEQyRWZ4NGJmZVEydTk5X2c&output=html
Maybe that solves your problem.