how do I un encrypt a document a document that pages encrypted

As SGIII stated. Otherwise, your password-protected document remains that way, as there is no higher authority that knows your password or can reset the document — unless you can retrieve an earlier version of the document from a Time Machine backup when it was without password protection.

You can prevent this in the future for documents that you set the password, by selecting the red-boxed option:

Future attempts to open this document, when the above is selected, will just open the document for you (while in your signed-in account, as the password is requested and provided automatically by the Key Chain.

Enter the password.

SG