OCRmyPDF

OCRmyPDF adds an OCR text layer to scanned PDF files, allowing them to be searched

To get the script usage, call: sh ./OCRmyPDF.sh -h

Main features

Generates a searchable PDF/A file from a PDF file containing only images
Places OCRed text accurately below the image to ease copy / paste
Keeps the exact resolution of the original embedded images
- or if requested oversample the images before OCRing so as to get better results
If requested deskews and / or clean the image before performing OCR
Validates the generated file against the PDF/A specification using jhove
Provides debug mode to enable easy verification of the OCR results
Processes several pages in parallel if more than one CPU core is available

I searched the web for a free command line tool to OCR PDF files on linux/unix: I found many, but none of them were really satisfying.

Either they produced PDF files with misplaced text under the image (making copy/paste impossible)
Or they did not display correctly some escaped html characters located in the hocr file produced by the OCR engine
Or they changed the resolution of the embedded images
Or they generated PDF file having a ridiculous big size
Or they crashed when trying to OCR some of my PDF files
Or they did not produce valid PDF files (even though they were readable with my current PDF reader)
On top of that none of them produced PDF/A files (format dedicated for long time storage / archiving)

... so I decided to develop my own tool (using various existing scripts as an inspiration)

Copy the file in onto your linux/unix machine and extract it.

Run: "sh ./OCRmyPDF.sh -h" to get the script usage

If not yet installed, the script will notify you about dependencies that need to be installed

In case you detect an issue, please:

Check if your issue is already known
if no problem report exists on github, please create one here: https://github.com/fritz-hh/OCRmyPDF/issues
Describe your problem thoroughly
Append the console output of the script when running the debug mode (-g option)
If possible provide your input PDF file as well as the content of the temporary folder (using a file sharing service like www.file-upload.net)

c't 1-2014, page 59: Detailed presentation of OCRmyPDF v1.0 in the leading german IT magazine (c't)