NOTE:
No changes can be made to a signed document. There is no way of unlocking a document without making your digital signature invalid.

Edit a signed document

To make changes after the document has been signed, you will have to create a copy of the document where you'll be editing in instead.

1. Make a copy of the document by clicking the three dots in the top right corner > Copy.
   
2. Enter a name for your new document.
3. Make your changes, save and send the document to your counterpart for a new signature.

Why do I have to get a new signature?

While you may think of it as "the same document" as before, changing any details will make it a completely new document requiring a new signature.

What do I do with the old document?

Either remove it completely or link the old document to the new document, read more about linking documents here.  You can also add a comment to the old document with a link to the new document.