When I publish my site using VSD, all of the pages are republished even if there are no changes to them. Is there a way to just publish one page at a time?

Far as I know, that should not happen and I can't find any setting for that. Unless your server is adjusting file dates or something then only new and/or modified files should upload.

I would contact Coffeecup via a Support Topic and see what they say. Just go to your name at the top right and scroll down to 'Your Support Room' to open a support topic.

Then post back here if you would and let us know what you find out.

Worth a try but instead of hitting the publish icon, go to top tool bar publish option
and select publish from there instead
I know from experience it often works different to the publish icon and it may well be due to windows version or similar
Also when VSD publishes it does check every single page looking for edits though it does not actually upload them again
I also discovered recently when changing hosting company that an edit to one page on my 68 page site now on average only takes 1 minute, with a previous host it often took nearly an hour

What your probably seeing is VSD scanning your site and comparing what's on the host with what's on your pc. If there's any changes on the page on your pc VSD will upload it.