Image-Only PDF
What an image-only PDF is, why it limits search and accessibility, and how to make it searchable.
An image-only PDF is a PDF whose pages contain raster images and no text objects. Each page looks like a document, but the file holds pictures of text rather than characters.
Because there is no text, the content cannot be searched, selected, copied or read aloud by a screen reader. Search engines and document indexes also see nothing on the page. File size depends on the image resolution and compression, so image-only PDFs are often larger than text-based PDFs of the same length.
OCR can convert an image-only PDF into a searchable PDF. The OCR engine recognizes the words and adds them as invisible text placed over the image, so the page looks the same but the text can be found and copied.
Image-only vs searchable PDF
| Image-only | Searchable | |
|---|---|---|
| Appearance | Page images | Same page images |
| Text layer | None | Invisible OCR text |
| Search and copy | No | Yes |
| Screen readers | Nothing to read | Can read the text |
How image-only PDFs are created
- Scanners and scanning apps with OCR turned off.
- Combining photos or screenshots into a PDF without OCR.
- Printing to PDF from software that rasterizes pages.
- Flattening a PDF to images to remove editable content.
How to tell if a PDF is image-only
- Open the PDF and press Command+F to search for a word you can see.
- Try to select a line of text with the pointer.
- If search finds nothing and selection draws a box over the whole page, the page is an image.
Common mistakes with image-only PDFs
- Sharing study notes or manuals that nobody can search.
- Assuming a PDF from screenshots is searchable without testing.
- Running OCR on low-resolution images and trusting the result without checking.
- Using image-only PDFs where accessibility is required.
Turning pages into a PDF?
Temposhot runs OCR when it exports a PDF from the results pane, so the file is searchable. See save screenshots as PDF on Mac, or convert existing images with Screenshot to Searchable PDF.
Common questions
Can I fix an image-only PDF without the original images?
Yes. Run OCR on the PDF to add a text layer. Accuracy depends on image quality.
Why can I not copy text from my saved ebook PDF?
The pages were probably saved as images. See cannot select text in a saved etextbook PDF.
Sources
Related resources
- Export formats: searchable PDF export.
- Extract Text from Image: copy text out of a single image.
Taking the same screenshots again and again?
Temposhot captures a screen, window or area on a timer and exports the set as a PDF, images, ZIP or MP4. The free browser tools fix single images.
Related resources
Related terms
- Searchable PDFWhat makes a PDF searchable, how to tell if yours is, and common mistakes when working with image-only PDFs.
- OCRWhat OCR is, how it works, where it's used, and common mistakes to avoid when making screenshots and scans searchable.
- Text LayerWhat a text layer is, how it gets into a document, and why it determines whether your PDF is truly searchable.
- Screenshot to PDFHow to convert screenshots to PDF, when to use single vs multi-page exports, and mistakes to avoid.