PDF

Scanned PDF

To reduce PDF size of scanned papers, add OCR and realign pages use ocrmypdf

For a scanned PDF, to reduce size, clean and realign pages, rotate-pages and add french OCR :

ocrmypdf --clean --deskew --optimize 3 --jbig2-lossy --rotate-pages -l fra --jpeg-quality 10 scanned.pdf output.pdf

You can play with --jpeg-quality to select a trade-off between quality and size from 1 (lowest size) to 100 (better quality)

You have to install tesseract-ocr-fra

sudo apt install tesseract-ocr-fra

For a regular PDF, to reduce size :

ocrmypdf --skip-text --optimize 3 regular.pdf output.pdf