Documents requiring new information added w/signatures monthly

[Shannon5E18]

We have a document we use that requires us to add a line each month itemizing expenses for client, and then they sign it. 
However, once we have sent it the first month and gotten the signature, we can't edit the document to add the next months expenses and get the second signature. 
Is there a way to set it up so that we can continue to use the same document each month. 

I attached a blank copy so it's easier to visualize what I am asking. 

[try67]

A signature locks the file, except for form fields, if it is set up that way. So you could add form fields to it and a signature field and set it to not lock those fields when signed, so you could edit them later on.

[MikelKlink]

To refine the form-field idea:

Surely you want data entered not to remain editable after signing, you merely want to allow adding new data.

Implementing this with form fields is possible: For each update of the document you can have a dedicated set of form fields including one signature field, and that signature field can be configured so that when it is signed, the data fields from the same set get locked but not the fields of other such sets.