Hi paolo-S,Do you know which third-party app was used to add protection to the PDF documents?Acrobat Reader mobile apps (iOS, Android, and Windows Phone) do not support third-party DRM (Document Rights Management) protected PDF documents. Example: "protectedpdf" by Vitrium (not Adobe)As a workaround, please use the desktop version of Acrobat Reader on a Windows or Mac computer to open the protected PDF documents.Sorry for the inconvenience.
I am not able to speculate on any future plans for the Acrobat Reader for iPhone and iPad app. However, Acrobat Reader mobile apps have not supported any third-party DRM technologies (such as "protectedpdf" by Vitrium Systems) in the past several years.
If you'd like, please submit a feature request using the following online form.