how to make a scanned PDF text-selectable using ghostscript and gsview

pdf

Neither of those will by themselves.

Scans are images. What you need to convert a picture of text to actual text is OCR. Ghostscript supports OCR with Tesseract. There's also a number of OCR applications, free and paid. One such freeware that utilizes Tesseract is OCRmyPDF, downloadable from Github.

Tests and recommendations can be found searching something along the lines of "best ocr applications".

There are also some websites that can do it, but the ones I've seen are either limited (for example to 3 pages without pay) or the quality has been terrible.

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