How to make a pdf file from scanned images

How to know if a PDF contains only images or has been OCR scanned for searching? I have a bunch of PDF files that came from scanned documents. The how to make a pdf file from scanned images contain a mix of images and text.

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83a8 8 0 0 0 0 7. 3A8 8 0 0 0 1. 77 0 0 1 4. Some were scanned as images with no OCR, so each PDF page is one large image, even where the whole page is entirely text. Others were scanned with OCR and contain images and searchable text where text is present. In many cases even words in the images were made searchable. Does anyone know if there is a way to tell which ones contain only images, and which ones already contain searchable text?

NET but I don’t think being able to tell the two kinds of files apart is language dependent. Use comments to ask for more information or suggest improvements. Avoid answering questions in comments. Scannned images converted to PDF which have been OCR’ed in the aftermath to make text searchable do normally contain the text parts rendered as “invisible”. The font ‘Arial’ is also used, but is not embedded.