Originally Posted by susan_cassidy
You can't sync books which are not purchased at Amazon. You can't sync via your PC, either.
Actually, you can sync books that weren't purchased at Amazon, as long as they are stored in your cloud (archives). You can send to the cloud by enabling archiving in the Personal Document settings on the Manage Your Kindle page at amazon.com. I believe that using the Send To Kindle app also sends documents to the archives, but I don't use that app, so can't confirm that.
Here's a link to the page on amazon that discusses this: