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Realizing The Best 6 Online PDF Annotators in 2024

Big businesses and companies always prefer a digital source for transferring data and information because they are efficient and convenient. But files also need editing as well, so for that, you need a good PDF annotator which has all the functions. In this article, we have discussed various online PDF annotators as well as recommended an alternative to it. Online tools have some limitations, so people shift towards offline tools, which are great for students, teachers, and other professionals.

Part 1: An Offline Alternative to Online PDF Annotator - UPDF Annotator

An all-in-one solution to your annotation problems is UPDF- PDF editor. People who don’t like to use online annotation tools because of the limitations and formalities they have tend to move towards offline tools. One exceptional offline tool is UPDF because it has all the features a person would need. The annotation tools offered by UPDF are highlighter, shapes, drawing tools, strikethrough tools, sticky notes, text boxes, stamps, etc.

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One of back to school tips - Using UPDF to improve your productivity

But with that, it also has PDF editing tools. It is a PDF commenting tool which works seamlessly; you can easily cut and delete the text, but when required, it also helps in adding new text. When you add new text, you can simply change the font style and size of the text. Even if you use a pencil tool, you can increase and decrease the thickness of the text. But with all that goodness, it also has a flaw in it that it doesn't have a web-based version. So, if you are a Windows or Mac user, we recommend you shift to UPDF.


  • Support desktop Windows and Mac, and mobile iOS and Android.
  • Powerful functions like edit PDF, annotate, convert, merge, combine, protect, flatten PDF and etc.
  • It has a beautiful and simple UI interface.
  • Has advanced features satisfy all the needs: OCR, add watermarks, background, header and footer, add electronic signature to the PDF, etc.

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Part 2: Top 6 Online PDF Annotators

Online PDF annotators are a source for editing your documents when required. They are the best when you are in a hurry and want to send out an official document. These annotators have the best annotation tools with a wide variety, so to have a look, you can read about the 5 annotation tools listed below:

1. LightPDF 

If you are a teacher who is busy preparing a syllabus outline for her students and want to add some essential points, then use LightPDF for your ease. LightPDF is a tool with various annotations like Comment, which facilitates a writer in adding depth, meaning, and additional information to their words.

The best part is that you do not have to download software before editing a file; just access the website and upload a file for editing. This online tool claims to be a secure platform for people, unlike many other free PDF commenting tools.

online pdf annotator


  • With the help of LightPDF, you can even edit the contents of your original PDF. You can customize the formatting, font, color, and images.
  • It has convenient accessibility because you don't have to make an account to use it, and it offers all the functions without acquiring the details of a login account.
  • LightPDF has an API tool that helps to convert PDF content into text very easily because it has a high conversion accuracy. It is helpful for people who are into business.


  • LightPDF's free API feature has a file size restriction as it doesn't support or edit a file larger than 5 MB, so people usually prefer other tools for editing.

2. zipBoard

zipBoard is a centralized PDF annotation tool that allows internal and external stakeholders to collaborate on PDF documents and leave contextual feedback.

With zipBoard's visual review and annotation tools - including pencil, comment, rectangle, arrow, highlighter, screenshot, and slideshow. - you're assured of a streamlined document review and approval process devoid of multiple share screen calls, long email threads, and lack of clarity in your PDF document reviews.

zipBoard helps you speed up your document reviews and approvals so you can hit your deadlines.

online pdf annotation tool zipboard


  • Kanban and spreadsheet views to keep issues and tasks organized in one place
  • Unlimited collaborators and projects
  • Customized approval stamp and signature to sign off on the PDF document
  • Multiple integrations (like Slack and Microsoft Teams) and APIs to integrate with your existing document management system
  • Flexible sharing options - share PDFs as a link with clients & collaborators
  • No downloads or extensions needed

3. Sejda 

Running a large business is not at all easy, and with that, sharing data and files becomes difficult too. In that case, you might have come across a situation where your client added some unwanted quotations, and you want him to remove that.

An easy way to tell him about removing those quotes can be by using the Strikethrough tool of Sejda online PDF annotation tool. This tool helps in cutting out the part of the document that is not required and works conveniently.

online pdf annotation tool


  • It has many editing options, but the best part is that it can convert images into a PDF format, and you can merge two files.
  • If you are unhappy with the text, comments, or remarks on the PDF file, you can easily erase the comments and remarks by using the whiteout option.
  • It is a very basic tool for a basic-level user and has all the features that are required to prepare a file, like a watermark. You can add your watermark to edited files and pictures.


  • It doesn’t offer many font styles, so it becomes difficult for the editor to find the most similar font to the one that is on the PDF.

4. PDF Bob

PDF Bob is an amazing online annotation tool for PDF for people who want all the features and functions in one place. If you are editing a PDF file and want to stay on a single tool for editing, you must access PDF Bob’s website. It has a wide range of editing and annotating tools, and the user enjoys using it.

You can use it for creating different diagrams and structures because it has various shapes like rectangles, ovals, etc. Add sticky notes by using PDF Bob to the digital notes you are making for your exams so that you don’t miss out on important points.

free pdf commenting tool


  • A great feature offered by PDF Bob is the Mange Pages which helps you to add new pages, rearrange them, merge files and delete unwanted pages.
  • It not only allows exporting a PDF file in PDF format but also supports JPEG and PNG formats.
  • It offers amazing freehand annotation tools like a pencil that can be used by children as well as adults to create something of their choice.


  • It has many features, but one of the most efficient and effective features, like sign PDF, is still missing. People who are editing their files have to shift to a new editing tool for using the E-signature feature.

5. PDFescape 

PDFescape PDF commenting tool is a versatile tool that offers its users different editing and annotating tools. Due to a variety in tools and their functionality, a user becomes comfortable and always prefers using PDFescape.

Editing a file is no more an issue for office-going people because you can open the file in PDFescape and add text, shapes, and comments to it as quickly as possible. Apart from annotating tools, it has amazing file converting and editing options, so you can call it an all-in-one tool.

online annotation tool for pdf


  • It has a great digital signature tool that comes in handy for people who cannot sign a file consisting of hundreds of pages.  
  • It works best for big and small-sized businesses and companies because of the comprehensive and cost-effective features it has a PDF reader.
  • It gives the users great annotating options like adding text, shapes, and whiteouts. You can encrypt your PDF file with a password protection feature.


  • PDFescape doesn’t offer a feature of merging multiple PDF files and also doesn’t support batch processing.

6. Soda PDF 

When we talk about a fully equipped web-based annotator that has variety and versatility in tools and other functions, we cannot forget Soda PDF. Soda PDF is an online PDF annotation tool that makes sure to provide a good user experience by editing, reviewing, and annotating files.

It ensures that the user's shared files and data are safe and secure. It entertains business officials well because it has all the tools that are required for editing an official file like e-signatures, etc.

pdf annotator free online


  • It is a multifunction PDF editor which converts PDF files to other formats, and also, you can prepare a professional digital form that is better than a handwritten one.
  • It is accessible through any Mac/PC and other gadgets like phones and tabs, so if you are on the go, you can easily edit a PDF file.
  • It offers an OCR tool that recognizes the text on the images and helps in adding it to the PDF. With that feature, it allows a user to create a custom toolbar in which you can add the most used tools.


  • Soda PDF has issues related to the response time because sometimes it doesn't respond to the user's instruction, and the user has to refresh the website resulting in the loss of the edits.

Part 3: Limitations on Online PDF Annotators

Online Annotation tools can be fun and easy but still require more attention because they need that extra struggle to use them. Internet connectivity is the main requirement to run an online annotation tool for PDF, but in case you have no access to the internet, then what? Then you suffer, and the internet connectivity issues become a root cause of other limitations as well.

If you don't have a strong internet connection, you would probably suffer from uploading a large-size file because, generally, this requires a fast connection. Also, when talking about file size, many web-based annotators don't support a large-size file, and a person may have to jump from one tool to another to upload and edit. Many web-based annotators don't provide a secure platform to the user, so people like to switch to offline tools as they are safer and need no internet connection.


Annotation is a necessity for a person who has all the file work. Since the world is changing rapidly and things are more digital now, PDF files need an efficient editing solution as well. For that purpose, we have listed 6 different types of PDF commenting tools.

One of them is an offline alternative to the rest of the 5 online tools. The user can use any of the online tools mentioned above, but people usually prefer offline annotation tools because of their versatility. UPDF is our recommendation to all Mac users out there.

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