The ability to create stunning documents using iWork (Pages, Keynote and Numbers) is only one of the reasons why iWork is a great tool for many home and small-to-medium-sized businesses. The ability to collaborate with others on a single document is another. This can be done with the click of a button within each app.
To share a document with someone else, simply click on the "Share" button, choose "Share Link via iCloud", then choose the method of delivery (iMessage, email, Twitter, etc).
That's it! Once the link has been sent, your document will be available for anyone with that link to open, view and edit the document.
If you want a little more privacy/security enabled for your shared document, there are options for that too. To enable these options, click on the "Share" button, then choose "View Share Settings...".
There are two options available here: Permissions and Password.
By default, the permissions for the file are set to allow others to view and edit the document. By changing this option to "View Only", you are allowing the other party to view the file, but make no changes. This is a great option for those who are just sending their documents out for review. If you choose this option, you (as the document owner) will still have full edit capabilities.
Setting a password for your document is a great idea in many cases, since the document can technically be accessed by anyone who has the link. If the document requires that level of security (due to confidential or sensitive information), I highly recommend sending a link to the file using one type of communication (iMessage, email, etc), and then sending the password using another (phone call, text, etc). That way, if someone does happen to pick up the link to the document, they won't also have the password.
If you do choose to set a password for sharing your document, it will not only require others to use the password, but you will also be required to use the password each time you open the file. That's because the file itself is now password-protected (not just a shared version). Having said that, do not forget the password.
To remove the password on a document, go back into the "View Sharing Settings..." options, click on "Change Password", enter the current password, and then click the "Remove Password" button. This will remove the password from the file.
With all of that in mind, there are some drawbacks to sharing iWork files via iCloud. The biggest drawback for me is the level of real-time collaboration. This feature doesn't work extremely well if you have two people using the file and making changes at the same time (if you need that level of real-time collaboration, you may want to consider using a solution like Google Docs). Outside of that (and considering that iWork for iCloud is still technically in Beta), I have found it to be pretty stable and feature-rich.