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.

The solution is to do everything digitally, scribbling your signature with your finger, a stylus, or a mouse cursor, and pasting it on the PDF.

You can always take a photograph of your signature written on paper using your phone and upload it as an image that way to be used when digitally signing your PDF documents, directly from the ...