Contraseña. Protection

Contrary to what some may believe, Adobe doesn't keep copies of passwords that users apply to PDF files. What protection would it be if Adobe was to maintain copies of passwords or have a back door by which you could open a password-protected PDF file?

Unless someone else actually applied the password, gave the PDF file and the password to you, and you can get the password from that third party, sorry, there is nothing that we can do to assist you.