Try Zotero. It is a complete literature databas but it's PDF reader is very good at extracting images and text. Works on all OS, web and mobile. Native Linux client has been very smooth for me. Oh, terminal it doesn't do though. If you want to extract a large amount in an automated way, its probably not the right tool.
gImageReader is a graphical front-end to the open-source OCR program Tesseract, so that might be just what you're looking for. The default settings don't add the OCR'd text to the PDF but you can do that.