In Adobe pdf Reader or later, open a. pdf file and choose Encrypt from the File menu. After selecting the encryption method, the file will be encrypted. Because the code part of the file is encrypted, copying and pasting will not affect the normal use of the file.

Add a valid digital signature to the file. The file can still be transmitted normally, but if the file is modified, the digital signature will be destroyed.

Restrict file read permission. If the file reading permission is set in the Windows operating system, as long as the user successfully copies and pastes the file to another computer, the file will lose its restriction; If it is restricted in Adobe PDF Reader, the restriction will still be valid after copying and pasting.

As can be seen from the above, unless the file is encrypted through the "single-user read permission restriction" function provided by Windows, the file will remain encrypted after copying and pasting and will not be destroyed.