Ok i've done a lot of research.
Here are the results:
ebookpro:
Features: Users view your 'ebook' via their application and each time they open it, it checks in on the internet to make sure they have the right to view it. This prevents sharing.
Cons: requires users to download an exe, install it, and download your ebook, and be on the internet when they want to read it, and they don't get to view it on the nice Adobe acrobat interface that we are all accustomed to.
dlguard:
Features: I installed it. It works good and has some tracking benefits. It's also very feature rich for members hip sites.
Cons: If you only have 1 product and you don't plan on making a member site and you just want to dispense one ebook, then it can't help you much beyond giving you a download link that dies after x number of downloads.
CBLockPro:
Features: A nifty litte php script that resides on your server and is programmed to only respond to the clickbank passcode when a users requests a download.
Cons: It 'hides' the product download by simply using an iframe. While this might fool the casual user, anyone who knows what they're doing can easily spot this.
pdflocker:
All it does is encrypt pdf files. But the new adobe acrobat pro has this feature built in anyway.
eJunkie:
Features: a very attractive easy to use website, clickbank integration. EJunkie insures that downloads are only available from people comming from clickbank. Also it provides a shopping cart with other features for physical products as well.
Cons: if you are only selling one product via clickbank, you could actually do this yourself with minor programming knowledge. But you need to know how to use the clickbank "Secret Key".
Conclusion:
Since my only goal is to:
- sell one pdf viewable in acrobat
- have a download link that is not globally accessible
then eJunkie is the way to go.
Unfortunately, this means that, once the pdf is downloaded once, it could theoretically be placed in an emule directory right away and gobbled up.
The only way to avoid this, that i can see, is to use ebookpro. But I just think the hassle is too much for me and the user.
Dream Product:
What someone should really make is this:
An instant download application that, once it receives the "buy" message from clickbank, generates a pdf and saves it with the encryption turned on. Additionally, the password for the pdf is the name of the buyer himself.
Thus, if he shares this pdf, eveyone will be forced to type in his first and last name to view it. Hence insuring that you will know the first person who seeded the piracy.