I've a scanned PDF and i can't seem to highlight the text of course using the preview on my OS X, is there a software that do that like in windows?


2 Answers 2


Highlighting text in a PDF assumes that there is text in the PDF to begin with.

When you scan a document to PDF, it is simply an image. You should still be able to use the annotation tools available in preview to draw on it and add notes, but you will not be able to highlight or copy text from it because there literally is no text in the document.

There is, however, a type of software called OCR, for Optical Character Recognition, that can be used to programmatically "read" the letters in the image of your document and write out accurate text to the PDF. Some of this software is pretty good, but it is rarely free. Some scanners come with OCR software, and the you may be able to find some software online that will let you try it out for free.

Running an image PDF through OCR software will provide it with text data that you can then highlight using the annotation tools in preview.

  • yeah i know that and i've tried it but the OCR softwares are expensive. My friend has windows and he has a software that can highlight anything and it does not need the text to be recognized. it simply draws a color on the part you want like in paint. but this software is for windows only. Is there anything like it for OS X?
    – M. AB
    Aug 5, 2014 at 13:18
  • So what you really need is the ability to draw semitransparent rectangles on a PDF image. Preview indeed can only draw opaque boxes, but there are a multitude of options out there. I've heard good things about (though haven't tried myself) PDFPen Pro. You may also find alternativeto.net to be a useful resource for other options.
    – NReilingh
    Aug 8, 2014 at 12:34

You can use ABBYY FineReader to recognise the text in the scanned PDF:

Create searchable PDFs ready for archiving

With a few mouse clicks you can turn paper documents into truly searchable compressed PDF files for archiving. Information in such archives can be easily retrieved at any time you need it by using keyword search, while document compression reduces the amount of disk space used. You can also save files to a PDF/A format for long-term archiving.

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