Inserting the Signature. In most cases, add signatures by opening the PDF document in Acrobat and then going to "File" and then "Add Text or Signature" or by clicking on the "Sign" button, which looks, not surprisingly, like a pen signing a piece of paper. Choose "Place Signature" and then pick the method, such as typing the signature or using. Esign a PDF Using Nitro PDF Reader Step 1:. If you haven’t installed the application, install it first. Step 2:. Go to the location where you have stored the PDF document copy (copy of the document you intend to sign). Step 3:. Next to the File option at the top of the page, hit the Home button..