How to Fix Acrobat Cannot Highlight Certain Text in a PDF
Question details
The user is unable to select or highlight specific text segments within a PDF document using standard annotation tools.
- Product
- PDF Editors
- Device & OS
- not provided
- Scenario
- Attempting to highlight text in engineering drawings, scanned documents, or PDFs containing specialized fonts.
- Observed behavior
- The highlight tool fails to select the text because the content is composed of raster images, vector outlines, or specialized stroke fonts that the software does not recognize as standard selectable text.
Before proceeding, check if you can select any other text in the document with your cursor to confirm whether the issue is isolated to specific sections or applies to the entire PDF.
Run OCR to Recognize Selectable Text
Use the Optical Character Recognition (OCR) feature to convert raster images and vector outlines into a searchable, selectable text layer.
A PDF editor's highlight tool generally works in two modes: one for actual text fonts and another for standard raster images. However, when dealing with vector-based letters or specialized stick fonts often found in engineering drawings, the tool cannot snap to the text. Running OCR creates a hidden text layer over these outlines, allowing standard highlighting to function.
Open the problematic PDF document in your PDF editor. Navigate to the tools menu and select the 'Scan & OCR' or 'Recognize Text' option.
Choose 'In This File' and select all pages or specify the exact pages containing the un-highlightable text.
Click the 'Recognize Text' button and wait for the software to process the document.
Select the Highlight tool from the comments or annotations menu again, and drag your cursor over the newly recognized text.
Use WPS PDF to OCR and Highlight Documents Seamlessly
WPS PDF provides a built-in, highly accurate OCR feature that quickly converts scanned images, engineering drawings, and vector outlines into fully editable and highlightable text.
- 1. Open the PDF: Launch WPS Office and open your scanned or vector-based PDF file.
- 2. Access the OCR feature: Go to the 'Tools' tab on the top ribbon and click on the 'OCR' button.
- 3. Process the text: Follow the on-screen prompts to extract text or convert the document, allowing the software to identify the unselectable fonts.
- 4. Highlight content: Navigate to the 'Comment' tab, select the 'Highlight' tool, and effortlessly mark up your document.
Frequently Asked Questions
Why does my cursor select a whole image instead of specific text?
If your document is a scanned image or a flattened PDF, it does not contain embedded text layers. You must perform Optical Character Recognition (OCR) to identify and separate individual text characters from the background image.
Does the highlighting issue happen with all engineering drawings?
Not necessarily. It happens specifically when the CAD or drawing software exports the text as vector paths (lines and curves) or specialized stick fonts rather than embedding standard system fonts into the PDF.
Can I highlight text on a secured or restricted PDF?
If a PDF is protected with a permissions password that restricts commenting, annotations, or content copying, the highlight tool will be disabled. You will need the correct permissions password to unlock these features.
How do I remove a highlight if I make a mistake?
You can generally click directly on the highlighted area to select the annotation and press the Delete key on your keyboard. Alternatively, right-click the highlight and select 'Delete' or 'Remove' from the context menu.
