is there a app that will let me digitaly let multiple people sign to a pdf document

There are meeting signin apps.

Apps to let you write on a pdf.

PDF Expert – the PDF handling app for the iPad. "It allows you to markup documents with highlights and handwriting, insert text and stamps, sign and even merge PDFs."

https://itunes.apple.com/us/app/pdf-expert-5-fill-forms-annotate/id743974925?mt= 8

iAnnotate – turns your tablet into a world-class productivity tool for reading, marking up, and sharing PDFs, Word documents, PowerPoint files, and images. Has a secure document edition designed for corporations.

http://www.branchfire.com/iannotate/

"ixelpoint technology allowed us to shrink the stylus tip size down to 1.9mm; 70% smaller than the nearest competition. While fingers and rubber styluses feel more like markers or crayons, Pixelpoint helped create a true digital pen. The tip’s material was hand-picked to mimic the drag of a pen on paper, giving you more control and better expression in every stroke."

http://adonit.net/pixelpoint/

You could look into

https://www.snappii.com/resource-center/challenge-create-mobile-apps-access-corp orate-databases-firewall-writing-code-opening-ports-firewalls/

From what I read snappii has a forms creation facility on the web. Once create the from, you download the app somehow.

Robert