Open the password-protected PDF document with Preview, then enter the password. To remove the PDF password on Mac, you can use Preview on Mac. How do I remove password protection from PDF? However, there is no guarantee that these programs can work. To remove unknown passwords from PDFs, you can try some PDF password remover programs that claim they can remove protections from PDF without a password.

If you don't know the password, you can't open an encrypted PDF file and thus you can't remove the unknown password from PDF with PDF editors like Wondershare PDFelement, Adobe Acrobat, or online tools like iLovePDF or Smallpdf.