Our Agree'nSign digital signature software saves time and money by allowing you to sign contracts online, using e-signature technology.
Link : https://www.agreensign.com/digital-signature.html
I have an Android application that generate a PDF with digital signature.
I use iText to create and sign document as this:
I search a PDF reader (android app) to read document and view digital signature. I only found this application:
https://play.google.com/store/apps/details?id=com.qoppa.activities.noteskey but it have bug with some certificates.