How to Highlight in PDF

Updated on June 13, 2019
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Katy shares her tech knowledge and research with anyone who wants to learn the smartest way to use technology.

How to Highlight a PDF

PDFs are a universal file type that everyone should know how to annotate, including highlighting. Adding highlight shows readers where to look for important information and can decrease the number of people who omit important information.

Here's how to highlight in a PDF in Adobe Acrobat:

  1. Open the PDF (you may need to right-click and select Open With... to select Adobe Acrobat).
  2. Click on Comment in the right-hand tool bar.
  3. Click on the Highlight Icon that appears at the top of the window.
  4. Highlight your text.
  5. Save the document.

This process works in most Adobe Acrobat products including Adobe Reader.

In many version of Acrobat the highlighter will already be enbled. You can see it on the top of your screen without clicking on the Comment tool.

If you're using a PC with Windows 10, 8 or 7 this will be the easiest way to add highlighting to your document.

Highlight a PDF in Adobe
Highlight a PDF in Adobe

Why Can't I Highlight Text?

On some PDFs you won't be able to highlight the text with the method above. This is because the program doesn't recognize it as text. Instead it thinks the area you're trying to highlight is an image or blank space. This will happen with scanned papers, they into documents that are not editable.

Documents that are actually images of text instead of real text can be a bit tricky. There are some paid options for converting them (see below) or you can get a bit creative with how you highlight or annotate.

Highlighting/Annotation Alternatives

There are other ways to add annotation to a PDF when you have an image of text:

  • Add arrows pointing to important information
  • "Highlight" words by outlining them with boxes
  • Circle parts of a document with the pen tool

Both Adobe's programs and many online programs offer the pen, boxes and arrows tools.

Example of how to highlight a scanned document with a box.
Example of how to highlight a scanned document with a box.

Edit PDF Documents Online

Sometimes you don't want to edit your documents while they're saved on your hard drive. Maybe your favorite program isn't installed or you just prefer to use an online tool.

There are many free online tools that let you upload your file, make changes and download the new version. PDFBuddy and LightPDF are very simple sites that let you do this.

The PDF will have to be recognized as a text document (ie not a scanned image) for those services to work.

DocHub with Google Drive

My favorite way to sign and comment on documents is through DocHub. i discovered them when uploading PDFs to Google Drive to share. When viewing a file on Drive there's a "Open With" drop down at the top and you can select DocHub. They let you store signatures that you can paste into your documents.

That was really helpful for me because I didn't have to print off something, sign it and scan it again. They also let you edit and highlight editable PDFs.

Highlight PDFs on Mobile

For the simplest way to highlight a PDF on your phone adobe has an app for Apple and Android. There's no ads and it's really easy to use. You can use other annotation tools like you do on the computer and save your files.

There are a handful of others apps that do this well also but they have ads and not all of them are easy to use.

Markup PDFs for Free

There are many free options to edit PDFs. It is such a universal file format you should never be paying to highlight text.

If you are trying to process scanned images as text to highlight or edit them then you'll likely need a paid software application. It will use Optical Character recognition to convert the image to text for you. then it will be editable just like a normal text file. Adobe's Acrobat (not the free "Reader" version) can do that for you as well as some paid programs online.

© 2019 Katy Medium


Submit a Comment
  • KCO profile imageAUTHOR

    Katy Medium 

    12 months ago from Denver, CO

    Hi Sam, I'm glad you like it! Thanks for sharing, I haven't used it but I'm sure that will be helpful for others who find this article.

  • Sam Gue profile image

    Sam Guevarra 

    12 months ago from Toronto, CA

    Hi there! I am very thankful for this post. I have also found out a PDF tool that can highlight PDF which is the ApowerPDF.


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