I made a site in VSD and uploaded via FTP. I have then made changes (SEO) to most pages via FTP. I would now like to bring the site back to my computer so that I can add pages in VSD. Can I do this and if so How?

You aren't able to bring the pages you've changed back into VSD, what you can only do is load the .vnu file that VSD creates. Once you alter things outside of VSD those changes can only be kept by continuing to alter outside of VSD. If you only did some minor changes and not a billion of them, you could copy the changes you made and put them into the .vnu file you last saved for the site and get it up to date that way, hopefully it isn't a lot of changes that would be lost. Shouldn't be too hard to update the .vnu file pages to the current outside changes you did as long as it's something possible to do in VSD.

That's about your only option if you want to get it back to VSD, it doesn't have a backwards setup that allows us to put pages back into the .vnu file, only allows us to export them out.
Sorry Huw, I'm sure that's not what you wanted to hear