There is an app called mobile OCR that turns scanned docs from your camera into text? not sure if you can then manipulate as a text document.
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I haven't used it on my S4 yet, but I used it extensively on my iPhone 5 and my iPod 4G for about 6 months for copying and OCRing old-style typed historical documents and spitting them out as PDFs.
As long as it translated over to Android OK, DocScanner should be magical with the S4's awesome camera and processing power.
A Freebie version is available but I have only used the paid one so am unqualified to comment.
I really liked the CamScanner.It is easy to use.You can first try its free version before buying a paid one.This app help you to auto-detect the edge of the paper and help you to tune the dimentions.
Thanks