20 Free Tools to Annotate PDF Documents

Do you use PDF files or read documents in PDF format? Even if you don’t use them regularly, I’m sure that you’ve come across a PDF file or two in your lifetime. They’ve been around for over 20 years and can contain links, buttons, form fields, videos, audio and more.

Reading PDF files can be done in many applications, but a lot of those apps don’t include annotation tools. In this post we’re going to focus on apps that do allow you to annotate PDF files. Whether you want to add text notes, bookmark a section, highlight or underline text, these free tools will allow you to do just that.

Shortcut to PDF annotation tools for:


Adobe Reader

This is the official Adobe Reader mobile application which works for the iPhone and iPad. It can also be used to fill out forms and electronically sign documents. With it, you can: highlight, strikethrough, underline, draw (freehand), comment (sticky notes) and add text using the typewriter tool.

Adobe Reader for iPhone and iPad

PDF-Notes free for iPad

This is the free version of the premium app pdf-notes; it’s available for the iPad only. Along with support for AirPrint, you can annotate your PDF files using a variety of pens, highlighters and text notes. It includes smooth finger writing and a palm rest so that there are no accidental marks on your documents.

pdf-notes free for iPad

AnnotDoc Lite

AnnotDoc is unique because it is the only iPad app that allows you to annotate Microsoft Word and PowerPoint files, on top of PDF files. You can also use it for highlighting, underling, watermarking, handwriting and adding signatures. The Lite version, however, does not support saving or exporting your documents, but you can take screenshots of your annotations.

AnnotDoc Lite for iPad

PDF Review Free

This is the free (try before you buy) version of PDF Review available for both the iPhone and iPad. The app allows you to leave feedback and notes on PDF documents. It helps simplify the review process of any file or document and allow feedback from multiple users. All feedback can be merged into a single list and you can even generate structured reports.


UPAD Lite is an advanced note-taking application with annotation features. You can handwrite notes, highlight text, add sticky notes and reference images. UPAD uses smooth retina ink, which results in beautiful, detailed handwriting. You can export any type of document as a PDF or PNG file by email or to cloud services like Dropbox, Evernote and Google Drive.

UPAD Lite for iPad


Mendeley is a companion app to the desktop tool for Windows. You’ll get your own digital library so that you can read, annotate and organize all types of files including PDF. Mendeley includes many features such as citation and bibliography generation, sticky notes and highlighting, importing and organizing PDF files, collaboration with a team, and much more.

Mendeley for iPhone and iPad


The free version of PDF Max is great for annotating, filling in forms and taking notes. At this time, it’s the only iOS PDF application that supports Adobe’s Rich Text Format Typewriters (aka FreeText). You can annotate by highlighting, underlining, crossing out and using "squiggly tools." It also supports addition of comments and threaded conversations, great for collaboration.

PDF Max for iPhone and iPad

DocAS Lite

The free version of DocAS lets you annotate PDF files, sketch ideas, create presentations, record audio clips and share notes. You can also access documents anywhere: PC/Mac desktop (via wifi), Dropbox, Box, Google Drive, FTP, WebDAV, other iOS apps and more. As well as PDF files, DocAS supports Microsoft Office and Apple iWork files, RTF, text and photos.

DocAS Lite for iPad


Adobe Reader

Just like Adobe Reader for iOS, the Android version lets you view, annotate, comment, fill out, electronically sign and share documents. It has all of the same features as the iOS app like freehand drawing, highlighting, underlining, etc.

Adobe Reader for Android

iAnnotate PDF

It’s very surprising that iAnnotate PDF for Android is free, especially since the iOS version is $9.99. You can open multiple PDFs using tabs, search through your documents and share them. iAnnotate PDF also supports Box OneCloud, which allows you to open files directly from and/or save them back to Box.

iAnnotate PDF on Android


Qiqqa is a research tool, much like Mendeley (see above). This is a companion app to the desktop tool [Windows], which lets you read and annotate your PDF files. With Qiqqa for Android you get: continuous scrolling, pinch-to-zoom, full-text search, annotations, bookmarks, tagging, cloud syncing, annotation reports, reference citing etc.

Qiqqa for Android

PDF Annotation

With a long press anywhere on your PDF document, you can add annotations. With PDF Annotation, you can also view a separate list of your annotations for easy reference. Although there is not much information provided about the app, a few user reviews suggest that it’s a bit restricted such as having no way to draw directly on the text or highlight.

PDF Annotation for Android

Mantano Ebook Reader Lite

Mantano is actually an eBook reader, but it includes annotation tools. You can use it to download eBooks from the OPDS catalogs and add your own catalogs. When it comes to annotations, you can: add text notes, highlight, share quotes and add bookmarks. By using Montano Cloud (paid subscription), you can backup your annotations and sync between devices.

Mantano Ebook Reader Lite for Android

qPDF Notes Demo

Although this is only a demo of qPDF Notes, it includes all features available in the full version; however, a watermark will be added to your PDF files if exported – which is fine for personal use or trying before you buy. With qPDF Notes you can add text, sticky notes and shapes to your PDF files. You can also highlight, cross out, underline, and sign documents.

qPDF Notes for Android

SmarQ Reader

Here is another PDF reader with annotation tools as well as page-cropping and sharing. There’s a built-in file manager for organizing and syncing your documents. You can add comments and highlights to PDF files in different colors and even pen sizes. There’s also a document manipulation tools for adjusting the brightness, inverting colors, adding texture and more.


Need annotation tools that work on the Web? Try these on for size.


A.nnotate is great for those wanting to annotate images, PDF files and Microsoft Office documents online. With it, you can add text notes, highlights and strikethrough. The collaboration feature with threaded comments and the ability to add tags to notes, makes A.nnotate great for freelancers, small teams and even businesses.

Annotate for Web


PDFescape is not only great for editing and annotating PDF documents, but you can also create new PDF forms, fill out PDF forms, password protect your files and share documents. With PDFescape, you can add text comments, shapes, images, sticky notes, and highlights to documents. Check out many other advanced features PDFescape has.

PDFescape for Web


GroupDocs is an advanced document collaboration tool that includes annotation features for PDF and Microsoft Office documents. You can add comments and mark up your text in real-time, much like documents in Google Drive. GroupDocs has 3 paid plans, and a free 14-day trial plan that lets you try before you buy.

GroupDocs for Web


PDFOnlineReader is not just for reading PDF files online. You can also add annotations, add hyperlinks and bookmarks, and highlight text. It’s a lot simpler to use and it’s great for those who want to annotate quickly, save and download their files. It also offers PDF desktop products for batch PDF creation and converting PDF files to other formats (and vice versa).

PDFOnlineReader for Web


This online document viewer lets you upload and annotate PDF files, Microsoft Office documents and images. With Crocodoc you can add text comments and drawings, highlight, and strikeout text on your documents. You can also use it to fill out PDF forms, collaborate in real-time and much more.

Crocodoc for Web

What do you use?

Now that we have shared 20 free PDF annotation tools for iOS, Android and the Web, it’s your turn. Do you use a free or paid PDF annotation tool? Which tool do you use and for which platform?

Want to learn more about PDFs? Read our Mastering PDF: 80 Free Tools, Tips and Resources.

via hongkiat.com http://www.hongkiat.com/blog/free-psd-annotation-tools/