Just some observations:
For purchased eBooks that are "PDF"; typically these have digital rights management (DRM) applied and must be used in conjunction with Adobe's Digital Editions rather than Adobe Reader.
A good practice to engage prior to install of a newer Adobe Reader - Uninstall the version being replaced.
I would like to read my purchased PDF's on my Sony eReader. That would be my preference. I can transfer them to the Sony reader either by using the Adobe Digital Editions software or the Sony Reader Library software. I can also read the books on my laptop with either one of those programs, and that's actually better than just using Adobe Reader because you can't even set bookmarks in Adobe Reader. Ultimately, though, I would prefer the convenience of the eReader. I've had one of the purchased PDF's freeze my reader occasionally, and another one was really bad. I'm just doing some trouble shooting with that issue, trying to rule out possible causes. I thought my having what could be considered an 'old' version of Adobe Reader might be a possible cause. I'm still working on this anyway.
Thanks again, so uninstall old versions first.