Hi all,
i'm testing my PAdES digital signature library in Obj-C and i encountered this kind of PDF file
http://dl.dropbox.com/u/3995257/PDF/Locked.pdf
Acrobat Reader tells that the document is locked by a signature (Signature2). As far as i know locked means that the file can't be modified but is is impossible to append a digital signature too?
I tried to sign the document with my lib and as expected the second signature invalidates the first.
http://dl.dropbox.com/u/3995257/PDF/Sign_Locked.pdf
But... i tried to sign for the third time the previous file. I would expect that the first (locked) signature would be invalid but the second and the third would be not.
http://dl.dropbox.com/u/3995257/PDF/Sign_Sign_Locked.pdf
Despite my expectations, only the last signature is avalid according to Acrobat Reader.
Does the first locked signatures invalidates the subsequents? Or more simply i can't sign a Document locked PDF?
Thanks