In Xodo Windows version 4.5.16, select "Save Copy", then "Encrypted"
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Using Xodo Windows Subscription, select "Actions", then "Security" | "Encrypt"
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Provide a password when prompted
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The document will open in a new tab. To confirm that the password works, you can close the tab and re-open it.
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The document will open in a new tab. To confirm that the password works, you can close the tab and re-open it.