These are but a few references to comparison shop for e-sign apps:
Gartner Group - https://www.gartner.com/reviews/market/electronic-signature
Digital Signature Application info compiled from various bookkeeper FB Group posts
Docusign - $19.80/month with a QBO Proadvisor discount (look in your QBOA Proadvisor tab)
Adobe Pro - $24.99USD/month - includes digital signatures
e-Sign Genie - Pay per use, no monthly subscription
One Span - Connects to Sharepoint - $20/month
Hellosign -$14/month, not included in Dropbox as originally reported.