A non-Adobe reader such as Foxit Reader might let you copy and paste. I remember that I could copy from a protected document in the Linux PDF reader (evince).
One thing that might work, which I haven't tried from Adobe Acrobat, is printing to a file. If you set up a dummy Generic/Text Only printer that has its output port set to FILE:, you can print to it, and it asks you for a text file to print to.