convert pdf to text using ocr

make sure you have imagemagick and tesseract are installed

$ sudo apt install imagemagick tesseract-ocr

It's a 2 step process:

1. Convert PDF to .tiff using convert from imagemagick

   $ convert -density 300 input.pdf -depth 8 output.tiff

2. convert .tiff to text using tesseract

   generate out.txt

   $  tesseract output.tiff out