In order to perform many operations, encrypted input PDF files must be decrypted. Some require the owner password, some either the user or owner passwords. Either password is supplied by writing user=<password> or owner=<password> following each input file requiring it (before or after any range). The document will not be re-encrypted upon writing. For example:
cpdf in.pdf user=fred reverse -o out.pdf
The password required (owner or user) depends upon the operation being performed. Separate facilities are provided to decrypt and encrypt files (See §4).