As @Eugenio Onofre already mentioned, it is not possible out-of-the-box.
However, there is a work-around if you are open to using an app. Our app Magic Labels has a feature that allows you to use hashtags # to add labels to your page.
With that feature enabled, you could type ##mylabel anywhere on the page to have that page labeled when you publish your changes. Using #mylabel also works and turns 'mylabel' into a clickable link; pretty much like on Twitter.
Anyway, hope that helps.