Hi!
Please let me introduce myself. I'm a web developer, specialized in backend programming, mostly in PHP, NodeJS and Java, with many years of experience in those fields.
Currently I have a working version of a software I named CatchCopy, and it works like what You described in your job posting. It parses the text into sentences and checks every single sentence on Google, Bing and Yahoo (howevery Google gives the best results). You can upload PDF, DOC and DOCX files, or You can copy the text directly to the website. It even sends you an email if the scan is completed since it can be time consuming and maybe You don't want to sit in front of the computer while it is working.
It uses UTF-8, so it can handle almost any text, including Greek and other European text. It even have multi-langual support, so You just need to add the translated files to it (it's just for the Web App User Interface, not the language it can parse and scan).
I can send You screenshots if You are interested in my software. Also, I can customize it for You if You need some changes in the functionality or design.
Feel free to contact me.
Regards!