I have a situation where I found a TON of scanned PDF files. These PDFs are effectively thin wrappers over a wasteful image format. Each file is several MB in size. The total size of the archive is over 1TB. I know there was no OCR work done... the PDFs only have the images, with not text layer or search capability.

I'd like to reduce the size of this archive. I know that if I had the original images, they would compress easily from 3-6MB each down to a few hundred KB each without noticeable loss of quality... a 10 times reduction in size. What I don't know is how to get back from these PDFs to the original image, how to recreate a PDF file from the reduced image (the user really likes PDF for some reason), and how to do all this in a reasonably automated way.

As an additional wrinkle, there are a few rare cases where some newer PDFs in the archive came from a separate and may have a searchable text layer that we don't want to lose.

Any ideas on how I can efficiently process these files?

  • pdftex reduce PDF size: reduce image quality? has a couple of ideas, e.g. using GhostScript. Do you have Adobe Acrobat available? – Andrew Morton Nov 11 '16 at 18:15
  • Please add an OS tag. There are various ways to extract images from PDF and process them in batch, e.g. pdfimages or mupdf on Linux. – dirkt Nov 13 '16 at 19:45
  • Only have the free version of reader. Running Windows right now, but may be able to copy files to linux to complete the task, so OS is flexible. – Joel Coehoorn Nov 21 '16 at 23:39

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