Now that college graduates are busy writing their graduation papers, have you ever thought that the papers you spent months working on might be "copied" and "pasted" into someone else's work? The way to prevent a copy of a work is to set up a copy-proof protection for your work.
The specific way is when their works are modified to implement the "tools" → "Protect the document", and then pop up a "Protection document" dialog box, in the dialog box to set the protection content to "form field", and then set the password, as shown in the last save the file.
Then look at the effect, the contents of the document can not be selected now, the "copy", "Paste" button in the toolbar has been restored, the Edit menu "copy", "Paste" also changed, "Copy", "Paste" function failure, can effectively prevent others copy.
This method is also widely used in making electronic documents to prevent others from intentionally tampering.