ebook Adobe Digital Editions protected files

I have a pdf with 1392 pages and it is protected.
It is readable only with the app from Adobe.
Ich which way use DT user protected files.
Is there a elegant way to handle this type of documents.

Is there a strategy for future or is it no problem ?


Is Preview able to open this file? Then DEVONthink (or at least the upcoming beta) should be able to open it too.

No, Preview don’t open the pdf.
I see only cryptic letters in right sidebar of Preview.