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I have scanned about 80 pages into gray scale pdf (image format). The end size of the file is about 70MB, which is very huge.

Now I am looking for a method to convert the grayscale image-based PDF file into a simple black/white text-based PDF file.

I have done many attempts with gs but with no success (only a few percent recovery). If any expert has some idea, kindly let me know.

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If you're interested in keeping the PDF images as-is and adding text to it, have a look at question Adding OCR info to a PDF. –  colan Sep 6 '14 at 13:22

2 Answers 2

You need some OCR tool. Look at Tesseract


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While this may answer the question, it would be preferred that you summarize or include key points to the linked page, should it disappear in future. –  Thomas W. Mar 14 '13 at 23:27

I guess you are using ubuntu. Search 'ocr' in ubuntu software center. You will get many image-to-text OCR softwares.

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