PDF Editing Issues

How to Fix Cannot Underline or Highlight Text in PDF on Android

Huma Ashraf Ch Oct 19, 2026 869 views

Question details

The user is unable to apply underline or highlight annotations to text within a PDF document using an Android application.

Fix: Cannot Underline or Highlight Text in a PDF on Android

Product: PDF Application
Device & OS: Android
Scenario: Attempting to annotate, highlight, or underline specific text in a PDF file on a mobile device.
Observed behavior: The highlight and underline tools do not work, text selection fails, or the application prevents applying annotations.

Before you start

Verify whether the issue occurs in all PDF files or just one by testing the highlighting tool on a different PDF document to determine if it is a document-specific restriction.

Solution 1Recommended

Check for PDF Password Protection and Restrictions

Many PDFs are locked by their creators to prevent editing or commenting. Checking the document security settings is the first step to resolving annotation issues.

If a PDF author sets up security restrictions, tools like highlighting, underlining, and text copying will be disabled by default. You will need to check the document's permission status.

Open Document Properties

Open the problematic PDF in your Android viewer, tap the three-dot menu icon in the upper corner, and select 'Properties', 'Details', or 'Document Info'.

Check Security Settings

Look for the 'Security' or 'Permissions' section. Check if 'Commenting', 'Highlighting', or 'Content Copying' is marked as 'Not Allowed'.

Remove Protection

If the file is restricted and you have the permission password, use the unlock feature in your app to enter the password and enable document annotations.

Check for PDF Password Protection and Restrictions

Scanned PDFs: If the PDF is a scanned image rather than text, you won't be able to select or highlight individual words without performing OCR (Optical Character Recognition) first.

Solution 2

Update or Reinstall the PDF Application

Outdated app versions often contain bugs that break text selection and annotation tools. Updating ensures you have the latest bug fixes and performance improvements.

Easily Highlight and Annotate PDFs on Android with WPS Office

WPS Office for Android provides powerful and user-friendly PDF annotation tools, allowing you to highlight, underline, and comment on your documents smoothly without compatibility issues.

1. Open PDF in WPS Office: Launch WPS Office on your Android device, tap 'Open', and select the PDF document you want to edit.
2. Access Annotation Tools: Tap the 'Tools' menu at the bottom of the screen, select the 'Annotation' tab, and tap the 'Highlight' or 'Underline' icon.
3. Select and Highlight: Drag your finger over the desired text to apply the highlight or underline instantly. Tap 'Save' when you are finished.

Free and intuitive PDF annotation tools for Android devicesHigh compatibility with standard Microsoft Office and Adobe PDF formatsBuilt-in OCR capabilities to help recognize and highlight text in scanned documentsLightweight app that combines PDF, Word, Excel, and PowerPoint tools in one place

Frequently Asked Questions

Why can't I highlight text in some PDFs but can in others?

The problematic PDFs might be restricted by the document creator to prevent editing and commenting, or they could be flattened image-based PDFs (like scanned pages) that lack digitally selectable text.

How do I highlight text in a scanned PDF on my mobile phone?

To highlight or underline text in a scanned document, you must first use an OCR (Optical Character Recognition) tool to convert the image into searchable text. Many advanced mobile PDF editors, including WPS Office, offer this feature.

Do I need a premium subscription to underline text in a PDF on Android?

No, basic annotation tools like highlighting and underlining are typically free in standard mobile PDF readers, provided the document is not password-protected or restricted.

PDF Troubleshooting