The Adobe Fill & Sign app is a free third-party app available on the App Store that provides a more polished and professional approach to signing documents on your iPhone.

We get all sorts of forms delivered electronically that need to be filled out and signed. This app makes it simple.

How to sign a PDF on an iPhone or Android using Adobe Fill & Sign If you're using an iPhone or Android mobile device to digitally sign a PDF, you'll want to download an app called Adobe Fill & Sign.

I have noticed that the app is incompatible with my Galaxy Tab 8.4 LTE, so let us know in the comments below if you have any other incompatibility problems when installing Adobe's Fill & Sign app.