Tried JCHUZI's work-a-round with a LOCKED pdf.
1. opened a "locked" PDF with ADOBE READER;
2. selected EDIT / SAVE AS . . .
3. chose txt, pdf, or word online to convert the file.
Note: When converted to TXT, the new file was unlocked and its content could be edited.
However, when converted (copied) as a PDF, the PDF stayed locked like the original and could not be edited.
P.S. I did not try the WORD conversion as that online service requires a paid subscription fee.
** using MBPro with LION and ADOBE READER