How to fill in and sign a PDF without printing it

First, does the form have fields?

Click in one of the blanks. If a cursor appears in a box, the PDF has form fields, and whatever you type goes into the field and is saved with the file. If nothing happens, the form is flat, usually a scan or a document printed to PDF, and you add text on top of the page where the answers go.

Some government and company forms are a third kind, called XFA, made with Adobe’s older form designer. They open properly only in Adobe Acrobat or Acrobat Reader; other readers show a page saying “Please wait” or that the document needs a newer viewer. If you see that, use Acrobat Reader for that form.

Filling it in

Free readers that fill fields and add text on top of a page:

• Adobe Acrobat Reader, with its Fill & Sign tool.
• Microsoft Edge, whose built-in PDF reader fills form fields and adds text and drawing.
• Preview on a Mac, which fills fields and adds text boxes from its markup tools.

Save, then open the saved file again, preferably in a different reader, to check the answers are really in it. Some readers keep typed text as comments, which other programs may not show.

A signature as a picture

The usual way to sign a PDF is to place a picture of a signature: typed in a handwriting-style font, drawn with the mouse or a finger, or photographed from one signed on white paper. Acrobat Reader’s Fill & Sign and Preview’s Sign both do it, and keep the signature for next time.

This is what most forms that say “sign and return” expect. Whether a picture is enough is up to whoever asked for the signature, and some documents, a will for one, need ink on paper in most places.

Keep the picture of your signature somewhere private. Anybody with a copy can place it as easily as you can, which is also why a picture proves little on its own.

When somebody asks for a digital signature

A digital signature is not a picture. It is a certificate, issued to you by a certificate authority or a national identity scheme, used to sign the file’s bytes. A reader can then show who signed and that the file has not changed since; change one character afterwards and the signature shows as broken.

Acrobat Reader can sign with a certificate if you have one. If you do not, the person asking usually means an e-signature service: they send you a link, you sign in the browser, and the service keeps a record of who signed and when.

Before you send it

• Open the saved file again and check that every answer and the signature are where they belong.
• If the answers must not be changed afterwards, print the filled form to a new PDF, which turns the fields into plain page content. Keep your own copy of the version with fields.
• Name the file so the recipient can tell it apart from the blank form.