It's not clear what role E-junkie would play in your scenario using DRM-X? From what I can tell, your buyers would need to have an account with Haihaisoft to pay for a license to open your protected PDF, which all happens within their dedicated PDF reader program, so we would not be involved at all in that.
I suppose you could use our Free Checkout to let each buyer order their file and have us issue them a download link to acquire their copy of your protected file, but this probably isn't even necessary and only adds unnecessary complication to the purchase process. Typically when a file is locked, the file itself is made freely available for anyone to download, since it's useless without paying for a license key to unlock it. You could just upload your locked file to your own Web site, and then post a link to download that file from a page on your Web site or in emails you may send to subscribers. Even Microsoft lets anyone download a copy of Windows to install, since it won't work without a license key from Microsoft.
We also don't have any way to handle recurring payments. If your product will be offered on a subscription basis, you might consider just using PayPal Recurring Payments as-is, either by itself or linked via PayPal IPN to a mailing list service such as Aweber and/or a membership management platform such as FrontDeskApp.