Why you cannot select the text in a PDF

▶ 1. Why the text cannot be selected

In the vast majority of cases there is a single reason: that PDF contains no text, but the photograph of a page.

This is what happens when a paper document goes through a scanner or is photographed with a phone. The resulting file carries the .pdf extension and opens like a PDF, but inside there is one image per page. The words you read without difficulty are, to a computer, merely light and shade: they do not exist as characters, so they cannot be selected, searched or copied.

The same applies to faxes, receipts digitised years ago and documents produced by older systems that print to an image.

🔍 2. Checking it in two seconds

Before looking for solutions it is worth making sure that this really is the problem.

1. Open the PDF with any reader and try dragging the cursor over a word.
2. If the word highlights, the document contains text: the problem lies elsewhere (see point 6).
3. If instead you draw a selection rectangle as you would on an image, you have a scan.
4. Cross-check: use the reader's search function and look for a word you can clearly see on the page. If it is not found, the text is not there.

◎ 3. Making the text selectable

Recognition adds text on top of the image: the look of the page stays identical, but the content becomes usable.

1. Install the extension from the download page and open the file with Choose a PDF.
2. If the Scanned pages detected window appears, carry on from there; otherwise open Local OCR.
3. Set the language of the document, or leave Automatic if you are not sure.
4. Click Run local OCR and wait for processing to finish.
5. Now try selecting a word: the text responds as in any other PDF.

📋 4. Selecting, copying, searching

Once the text has been recognised, all the operations that were failing become available again.

• ✓ Copy and paste a paragraph into another document.
• ✓ Search for a word across the whole file, useful on long documents.
• ✓ Highlight the important passages, as explained in the guide on how to highlight a PDF.
• ✓ Edit the text properly: see the guide on how to edit text.
• ✓ Archive the document as a searchable file, so you find it by searching for a word instead of remembering the file name.

⚖ 5. If recognition gets something wrong

No OCR is infallible, and the quality of the result depends almost entirely on the original scan.

• ✓ Set the right language instead of leaving the automatic option: it greatly reduces errors on accented letters.
• ✓ Straighten crooked pages before recognition, using rotation in the pages panel.
• ✓ Check the resolution: below 200 DPI errors multiply, 300 DPI is the usual reference for text.
• ✓ Double-check numbers and codes: a zero read as the letter O slips by easily.
• ✓ Handwriting stays out of reach: OCR reads printed characters.

◆ 6. When the PDF is protected instead

There is a second, less frequent reason why selection may not work.

Some PDFs do contain real text but carry restrictions that forbid copying: these are the permissions set by whoever created the document. In that case the text highlights but copy and paste produces nothing, or the reader explicitly warns that the operation is not allowed.

That is a choice made by whoever produced the file, and it should be respected. If you are the author of the document, you can review the settings following the guide on how to protect a PDF, where the Allowed actions section governs text copying.

? 7. Frequently asked questions

The questions that come up most often on this topic.