Why You Can't Highlight Text in PDF Documents and How to Fix It

Highlighting text in PDF documents is useful for placing emphasis on important keywords and phrases, aiding readability, and helping readers navigate different sections of the document. Sometimes, users can't highlight text in PDF documents, and there could be a few different reasons for this. Read on to discover the solutions to these common problems with highlighting in PDFs.

Why You Can't Highlight Text in PDF Documents

There are a few different reasons why you might be struggling to highlight text in a PDF document. Whether you're using a document for study, work, or leisure, highlighting text is a useful feature that might not always be accessible, But there's good news! UPDF can solve all of your highlighting woes in just a few simple steps. If you're thinking 'I can't highlight text in PDF files', then it might be due to one of these reasons:

The document is a scanned PDF

The most common reason that you can't highlight PDF documents is because the document doesn't actually contain any real text. Instead, it contains scanned text, which is essentially an image of the text. In this case, you won't be able to highlight, underline, strikethrough, or edit this text in any way.

Solution: Optical Character Recognition (OCR) technology converts text within images to real text. UPDF has the best OCR technology on the market; use it to convert your scanned PDF to real-text PDF in just a few clicks.

Also Read: How to Highlight Scanned PDF?

The document is secured or protected

If you are not the author of the file, then there may be some protections in play that do not allow you to highlight the file. To keep the PDF document secure, the author or distributor may have disabled edits and comments, which means that those viewing and using the document cannot highlight text on it.

Solution: Contact the author of the PDF file and ask them to enable commenting on the document, or to send you a new copy of the document with editing enabled.

The document is encrypted

Encrypted PDFs, such as ones with password protection or certificates, are not always editable on mobile devices. If you find that you are unable to highlight text in PDF documents on an Android, iOS, or another mobile device, but you can on your desktop device, then this might be the reason why.

Solution: Open your PDF on a desktop device, like a computer, to highlight text and make other edits.

Your PDF viewer does not allow highlighting

Another reason why you might be unable to highlight text in PDF files is that the PDF viewer that you're using does not allow highlighting. This might be because you need a paid version, or because your PDF can't highlight text - the viewer is out-of-date.

Solution: Download UPDF today - the best PDF editor available for highlighting, commenting, annotating, and more. Use this cutting-edge platform as your staple PDF editor for work, study, or leisure. With a beautifully modern user interface and super-fast processing speed, it's the only tool you need for all your PDF editing needs.

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The document is corrupted

If you can't solve your PDF highlighting issue using any of the methods above, then your file might be corrupted. This is especially likely if you downloaded the PDF from an untrustworthy source.

Solution: If you can't highlight PDF documents, try downloading the file again from a different source, or contact the file author for assistance.

An All-in-one PDF Editing Solution for Fix Unable to Highlight Text in PDF

If you frequently need to highlight text or make other annotations in PDF documents, then you may find a PDF editing software like UPDF to be a useful addition to your toolkit.


To highlight or comment on your PDF document you'll use UPDF's annotation feature. Using this can make your document more readable, making important parts of text stand out amongst the rest. You can annotate your PDF with stickers, stamps, signatures, and more using this handy tool.

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With UPDF software, you can edit any part of your PDF document including the real text, images, links, background, watermarks, headers, and footers. This means that you can change any elements of your PDF easily and quickly.

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OCR technology

With UPDF's Optical Character Recognition (OCR) technology, you can convert scanned PDF documents into real text documents, which will unlock editing and highlighting access. If you frequently scan documents from customers, colleagues, or friends and family, then you'll find this feature invaluable.

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Compression and Conversion

Sometimes large PDF files are a nuisance to share or upload. It's often a good idea to compress or flatten your document using UPDF's advanced compression tool. You can also easily and quickly convert your PDF file to other popular formats like PNG and Microsoft Word.


If you want to summarize, explain, or translate the text within your PDF document then look no further! UPDF Artificial Intelligence (AI) is your own personal assistant. This advanced feature can help you digest large blocks of information, summarize it for sharing, or translate it so you can share it internationally.

We invite you to download UPDF today and try the software out for free to see all of these fantastic features for yourself. Upgrade to UPDF Pro with a big discount. If you want to see a full review of the UPDF can be viewed on TECH ADVISOR.

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Frequently Asked Questions about PDF Can't Highlight Text

How do I enable highlighting text in PDF?

You can enable highlighting text in PDF documents by installing a new PDF viewer, like UPDF, and using the OCR technology, or by contacting the author of the PDF for permission to edit. Check more details about how to highlight scanned PDF here.

Why can't I highlight text in PDF in Acrobat?

There are five common reasons why you can't highlight text in PDF documents in Acrobat:

  1. The PDF you're trying to highlight is a scanned document;
  2. The file is secured or protected;
  3. The file has been encrypted and can't be edited on mobile devices;
  4. Your Acrobat PDF viewer doesn't allow editing; or
  5. The file is corrupted.

Why can't I select text in Preview?

The most common reason why you can't select text in Preview is because your PDF document doesn't contain real text, it is a scanned image of the PDF. To select text in a scanned document you first need to change it to real text using UPDF's OCR feature.

How do I turn on highlighting in Preview?

Here's how to turn on highlighting in Preview:

  1. Open your document by pressing right click and selecting 'Open with Preview'.
  2. From the top right corner of the page, select the highlighter pen icon.
  3. Select your text for highlighting and apply.
  4. Save your document to keep the edits.

Why is my Mac not allowing me to highlight text?

Your Mac might not be allowing you to highlight text because the 'Text Selection' tool isn't selected, or because your PDF is password-protected. Select Tools → Text Selection and then highlight your text as required. If this doesn't work, contact the author of the document to ask them for the password.


Now you're able to troubleshoot your highlighting issues with your PDF documents. Whether your PDF is password protected, scanned, or encrypted, you now have the knowledge to highlight text successfully. Your one-stop shop for all things PDF editing is UPDF. Download the UPDF software with a free trial today to unleash the power of PDF annotation, editing, AI, and OCR.

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