copy and paste blocked in pdf file

If this is a PDF that you have created, then in Preview, press ⌘+i to open the Inspector. On the toolbar of that Inspector is a lock symbol which is the encryption tool. Click that and you should see a panel:

Click the Edit button and you will see the following:

Since you do not want the PDF with a password, omit the Require Password to Open document section, and then deselect Copying Text or Graphics. Then enter and verify a password under Owner Password and then apply. Anyone attempting to copy/paste from this PDF will be blocked with a password challenge and your goal is met.

If this is a PDF that you did not create, it may have the original Author's password on it for opening the document, or their permission password for any of those items they wanted to restrict. If neither password is present, you can pursue the above guidance for applying your own restrictions and password. Otherwise, you will need to communicate with the original author of the PDF for access permission.

Hi here to help!

Ask the owner for an unsecured copy.

"* If this option is dimmed, make sure that the file you have open is a PDF. Some encrypted PDF documents can't be merged. To check the permissions of a PDF, choose Tools > Show Inspector, then click ."

Check permissions of file.

You may not have authorisation.

Kind regards

Rr