Smart phones are becoming ubiquitous and more powerful (just as Moore’s Law would suggest). With the increased processing capabilities and upgrades users are starting to demand the ability to do certain things that they used to do on their computer. Viewing PDF documents simply is not enough anymore with the need to sign them becoming apparent.
Adobe created Adobe Reader app which allows users to open, view and sign PDF documents from email or when integrated from Dropbox and Google Drive.
OK, so you want to stamp your document. Maybe you need to give reviewers some advice about the document's status or sensitivity. This tip from author Ted Padova demonstrates how to add stamps with the Stamp Tool along with related comments.