Trying to Edit a Document that has already been digitally signed/ modified

[Bow Tie Guy]

I had Nitro Pro 11 on an old laptop.  I just purchased a new HP laptop, and I transferred Nitro to it.  On my previous laptop, I was able to edit a document after it had already been digitally signed through ZipLogix, which is similar to Docusign.  I could insert and delete pages; I could add dates of execution, etc.  Now, when I open a digitally signed document in Nitro Pro 11,  the "type text" option is grayed out, and so is the "delete/insert" options.  I don't know how to resolve this issue.  Can anyone help?   Thank you!