Since upgrading to El Capitan I can't combine my pdf files or add pdf pages to a pdf document. Says the file is protected and cannot be used for this command. I haven't added passwords to any of my files. I'm using MAC OSX 10.11.1 and Acrobat Pro X1 v 11.0.13. I upgraded Acrobat from 11.0.12 today hoping that would fix the issue. The install went ok until near the end when I got an updater message saying the update could not be applied because the application contents were modified since the original installation. Adobe says I'm running 11.0.13 though. Any help most appreciated.