One of my colleagues who had such a PDF file, it was created by someone else and protected in this way. Unauthorized people can open and read the PDF without any problems, but they cannot copy and print the content. There are some online services can remove PDF security. For example, you can go to
PDF password remover. All you need to do is browse and upload the PDF files you want to unsecure to
remove PDF PasswordAnd click "Do it" button. After a few minutes, you will get a download dialog box, where you can save the unlocked PDF. But since your PDF is secured, online service is not that reliable, right?

To make secured PDF editable, desktop software called
PDF Password Remover for mac can help. The restrictions of editing, copying and editing will be removed immediately after decryption. This only works for PDFs that you have the legal rights to open and view.
PDF editor for maccan edit PDFs that require a password to be viewed cannot be unlocked. There is not any file size limitations, and you can batch process lots of PDF at one time.