You need the password for the pdf to change security settings. With Adobe Acrobat Pro the procedure I've used is:
- Open the pdf
- Go to File- properties
- Click on the Security tab and see Security Measures box for type of security; If password protected you must have the password to change security. Try anyway because occasionaly, RARELY, it works without your having the password. Also, look at the Document Restrictions Summary displayed on the page to see what actions are allowed with the password security
- If you can't change the security try printing the pdf to a non-Adobe printer and scanning the printed version to be saved as a pdf file on your device or the Adobe Cloud depending upon where you file your pdf's. I have done this several times with documents.