Inserting Add page a section expansion

I am very new at PHP, and PHP runner. I am working on a screen that will let me offer clients documents to sign agreements.
Big picture:
A user will have a see a list of documents they need to sign, With their credentials they can only see the list of documents and click on view. When they click on view, I want the document to open and a signature box to appear. The clients have read only rights to the documents but can write to the signature file.
Details:

I have the document table working and I have the signature table working. i just want a signature add box to appear under the document display.

The signature table is a detail detail item of the documents table.
I have tired copying the table under the signature -> add screen and pasting it into a section on the view document page. That didn't work.

How do I get the add signature detail screen to display on the view document scree either underneath the document or better in a section on the page.

is there anything special I have to do then to get the document ID's reference number into the Signature table item?
Finally I have to execute an update on the document status field in the document folder to indicated that is has been signed. That part looks pretty easy though I haven't looked at it yet.
Sorry for such a basic simple question.