A great idea that doesn't really work.
So much promise and very little of it delivered. I have had FlipBuilder's Flip PDF Professional (Mac) for several years. When it works, it is amazing. Problem is, it more often doesn't work. And customer service is spotty at best. If your problem is easy, Flipbuilder (Lynn Tang) is pretty quick to respond and provide support. However, if your issue is too complicated they just ignore you, literally. No return email saying they are looking for a fix, they just ghost you. You are left to fend for yourself or just not use the software.