The trick is to make sure that you have authorized an account (an AdobeID) in Desktop Adobe Digital Edtions
before using Sony eBook Reader. If you do things in this order, your Sony ebooks will use the same AdobeID and will work on your PocketBook (don't forget to authorize this in Desktop ADE also). Under Windows, the Sony ePubs download into My Documents\My Books\Reader Library. You should be able to copy them directly to the PocketBook, but if that does not work try importing them into Desktop ADE and transferring from there.
The above assumes you keep the DRM, but I suggest you strip the Adobe DRM and use FBReader on your PocketBook. See
Adobe ADEPT DRM for EPUB circumvented (note that Apprentice Alf's Blog has the latest info). Even if you end up using mobile ADE for ePubs on your PocketBook, DRM will bite you eventually unless you immediately remove it.