You can limit access to a PDF by setting passwords and by restricting certain features, such as printing and editing using Adobe Acrobat Pro DC application. However, you cannot prevent saving copies of a PDF. The copies have the same restrictions as the original PDF. Two types of passwords are available:
Document open password: A Document Open password (also known as a user password) requires a user to type a password to open the PDF.
Permissions password: A permissions password (also known as a master password) requires a password to change permission settings. Using a permissions password, you can restrict printing, editing, and copying content in the PDF. Recipients don’t need a password to open the document in Reader or Acrobat. They do need a password to change the restrictions you've set.
If the PDF is secured with both types of passwords, it can be opened with either password. However, only the permissions password allows the user to change the restricted features. Because of the added security, setting both types of passwords is often beneficial.
You can prevent users from changing PDFs. The restrict editing option prohibits users from editing text, moving objects, or adding form fields. Users can still fill in form fields, sign, or add comments.
To know how please check out the steps shared in the help page - https://helpx.adobe.com/acrobat/using/securing-pdfs-passwords.html#id_20302