Signaturely - Super simple eSignature software
Anvil PDF Filling API - The easiest way to programmatically populate any PDF
SignFree - E-Sign unlimited documents for freeSign in less than 30 seconds.
PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request
PlutoPDF - A URL to PDF converter wrapped behind a simple API.
DottedSign - The Best E-Signature Solution for Your Business