How to make a PDF searchable

First, check whether it needs it

Open the PDF and press Ctrl+F (Cmd+F on a Mac). Search for a word you can see on the page. If the search finds it, the PDF already has text and there is nothing to do. If it finds nothing, or your cursor draws a box instead of selecting words, each page is an image.

That is normal for anything that went through a scanner, a phone scanning app or a fax. The scanner saves what the page looks like, not what it says.

Make it searchable in four steps

1. Choose your PDF on the OCR PDF home page, or drop it on the box.

2. Pick the language the document is written in. The reader uses it to recognise words, so the right choice matters. See which languages it reads.

3. Press Make searchable. Each page is drawn and read in your browser tab. A progress bar shows the page it is on.

4. Download the result, open it, and try Ctrl+F again. You can download the plain text as well.

What actually changes in the file

A searchable PDF keeps the original page image on top and puts a layer of text underneath it. Each word in that layer sits where the printed word is, so when you search, the right spot lights up, and when you drag across a line, you select real letters.

Nothing visible changes: same pages, same order, same look. That is why this kind of file is sometimes called "searchable image" in Acrobat.

Four kinds of PDF

This tool turns the second kind into the third. If you need the fourth, see getting the text out of a scanned PDF.

If search still finds nothing

• The wrong language was picked. A German page read as English loses every ü and ä, so a search for “über” finds nothing. See the example, then run it again with the right language.
• The word is split across a line. A word broken with a hyphen at the end of a line is stored as two pieces. Search for the first half.
• The scan is too low in resolution. Tesseract works best on 300 dpi scans; at low resolution small print turns to blobs and the reader guesses. Rescan at 300 dpi if you can.
• The text is handwriting, or part of a picture. Tesseract is built for printed text and skips most of both.
• Your PDF viewer is searching another file. Open the downloaded copy, which ends in “(searchable).pdf”, not the original.

Other ways to do it

Acrobat is the better choice if you already pay for it and need to edit the text afterwards. OCRmyPDF is the better choice if you are comfortable in a terminal and have hundreds of files.

When the scan is a whole book

Reading happens in your browser’s memory, so this tool stops at 50 pages. A 300-page book also tends to have grey paper, dark edges and crooked pages, which cost accuracy. FixMyScan cleans and reads whole books on its servers, up to 1,000 pages.

Questions