You can fill out forms and sign documents that you receive on your iPhone. After you complete a form, you can add your signature and share it with others.Use the Notes app to scan documents and add signatures on your iPhone or iPad. Scan a document Tap Save or add additional scans to the document. One easy way to scan a document using your iPhone is through the preinstalled "Notes" app you will likely find on your home screen. Simply open the PDF file on your iPhone or iPad. If you're prompted to save the document in the Files app, choose a folder and tap Save. Election Forms and Tools for Sending. Using an iOS device? You can use Apple's Notes app, which also serves as a PDF scanner.