Sign a PDF from your smartphone

Add your personal signature to a PDF with the Microsoft 365 app for Apple or Android devices.  You can sign a PDF and save your signature for quicker reuse with other documents.

This is a useful trick if someone sends you a document to be signed. Instead of printing, signing then scanning the signed paper to email back, just sign the PDF on the screen and send it back.

Surprisingly, it’s easier to sign a PDF with Microsoft apps on a smartphone or tablet than it is with Microsoft products on Windows or Mac.  Signing a PDF is possible via Word but it’s a clumsy process of converting the PDF to Word then back again. See Make a better PDF from Microsoft Word using the hidden options

Digital Ink Signature

We’re talking about a digital ink signature, just as if you printed out the PDF then signed it with a pen. Not ‘digital signing’ a PDF or Office document which is a different thing entirely and done when the file is originally created.

Start from the Microsoft 365 app, download for iPhone, iPad or Android devices.

Sign a PDF

Either go to Apps | Sign a PDF or open a PDF then choose Sign PDF from the More … menu.

  • Tap on the screen where you want the signature to appear.
  • Choose ‘Create New’ (you’ll have the choice to save each signature or not).
  • Use your finger or stylus to write a signature (or whatever you like).
  • Choose from black, blue or green ink.
  • Add an image (corporate logo?) to the signature.
  • Delete to start over.
  • UNcheck the ‘Store Signature’ option if you do NOT want the signature saved.


After inserting a signature, it can be resized using the handles.

Repeat signatures

Sign the same PDF in several places via the ‘Sign in additional places’ button.

Saved Signatures

For future PDF signings, the list of saved signatures will appear automatically.

Save the signed PDF

An already saved PDF is automatically saved with the signature included.

If the PDF isn’t already saved separately (e.g. it’s been opened from an email attachment), the signed PDF will be saved to a nominated folder (e.g Device |  Documents | Microsoft 365 | Signed PDF)

Where are signatures saved?

The big question is, where and how are the signatures saved?  Are they saved on the device only?  Or saved to Microsoft’s cloud?  Are the signatures shared across Microsoft 365 apps for that user (that would be useful)? 

Wherever they are saved, hopefully the signatures are securely stored.  It would be nice to see that confirmed.

Microsoft is silent on this important point of customer privacy and security (sadly, all too typical).

What about date and time?

Aside from proper privacy disclosure (don’t hold your breath) the only thing missing from the ‘Sign a PDF’ feature is a quick way to add the date or date/time. That’s often required along with a signature but there’s no simple way to do that, except by ‘writing’ it each time.

Who gets it?

Signing PDF’s is currently in the Microsoft 365 app, Insiders releases:\

  • Apple iOS: v2.72 build 23041202 or later
  • Android: build 16.0.16327.20270 or later

More PDF support

The Microsoft 365 app (formerly the Office or Office ‘all in one’ app) has more PDF support.

  • Make a PDF from any Office document (Word, Excel or PowerPoint).
  • Take camera pictures (scan) direct to a PDF which can include ‘image to text’ conversion.
    • In my view, Microsoft Lens app is better for ‘scanning’ documents and converting to a PDF, but the M365 app will do the job.
  • Select existing pictures to make a PDF.
  • PDF to Word document.

Microsoft Lens

To use a smartphone camera as a scanner for documents or ‘image to text’ I still prefer the separate Microsoft Lens app over the Microsoft 365 app features.  Lens is easier to use with a clearer interface.

Microsoft Lens for iPhone/iPad iOS or Microsoft Lens for Android 

Make a better PDF from Microsoft Word using the hidden options
Two ways to read PDF files on an iPad
Three ways to add a PDF into a Word document
Free PDF combine, merge or splitting files
Show markup and comments in PDF made from Word