Often the Error its a problem with the File itself. Have you try to Download? If not work should check the File over the Reseller of the eBook.
Similarly to the handful of others getting E_ADEPT_OPEN_DOCUMENT_ERROR on Windows 10 and ADE; However, this was only on large pdfs (>350MB) when being delivered via .acsm. Smaller pdf and epubs download fine, whereas the larger ones get anywhere from about 10% to 60% before stalling and giving the error.
Trying to download with ADE 2, 3, and 4, and running each as Administrator didn't help. In hopes of helping someone else (as nothing apart from ADE appears able to deal with .acsm pdf), what seems to have done the trick was navigating to the ADE shortcut, right clicking it and selecting properties. From there selecting the "Compatibility" tab, and switching on "Compatibility mode" with "Run this program in compatibility mode for: Windows 7". Once in this mode, pdfs seemed to download without problem.