paper scanning software c# .net

Most scanners that work with Windows use either Twain drivers or WIA drivers, and many support both types of drivers. If you don’t know the differences between them, you can refer to this post:
http://support.leadtools.com/SupportPortal/CS/forums/7717/showpost.aspx

If you’re going to use WIA, you can try this Open Source project here:
http://www.codeproject.com/Tips/792316/WIA-Scanner-in-Csharp-Windows-Forms

If you want a free library that supports Twain scanning, you could try this one:
https://sarafftwain.codeplex.com/

There's a console application I made that uses LEADTOOLS SDK to scan a page, recognize the text and save the result as PDF:
https://www.leadtools.com/blog/document-imaging/ocr/scan-to-pdf-console-25-projects-25-days/
Disclaimer: I work for LEAD.