I wrote a blog post a while back that describes exactly how to enable canonical URLs for Sitefinity pages. I also include a video in the post that shows how all of this is done.
Also, you can disable canonical URLs per page. Just follow my simple steps below to disable a canonical url and add your own.
- Log on to the back-end of your Sitefinity web site (example: http://www.yourdomain.com/sitefinity).
- Click on "Pages" in the top navigation
- For the page you want to disable canonical URLs, just click Actions > Title & Properties.
- On the "Edit a page" screen, scroll down to the "Advanced options" section and expand it if it is collapsed.
- Set the "Canonical URL" property to "Disabled"
- If you want to supply your own canonical URL, just copy the canonical tag HTML below, paste it in the field "HTML in the <head> tag (except title, keyword, description)", and set the URL to your own custom URL.
<link rel="canonical" href="your custom url here" />
Hope this helps.