Fill is described as 'Makes it super easy to complete your PDF form. It is built to work like Google Docs for PDFs. Sign documents yourself, or send them to one or more other people to sign. Download your completed forms as PDFs, or email them directly to colleagues' and is an website in the office & productivity category. There are more than 25 alternatives to Fill, not only websites but also apps for a variety of platforms, including SaaS, iPhone, iPad and Android apps. The best Fill alternative is DocuSeal, which is both free and Open Source. Other great sites and apps similar to Fill are Nitro PDF , OpenSign, Docusign and LibreSign.