PDF document has never been intended to be edited. It’s intended to be a portable document format that can be open in a wide range of devices and platforms. However, it doesn’t mean that you can’t edit a PDF document at all. If you want to add some annotations, it’s possible to do so.

For a certain reason, you probably want to annotate your PDF documents. Like adding notes, highlighting certain sentences and so on.

If prefer to use an online tool to annotate your PDF documents instead of desktop-based one, following are several tools you can try.

1. PDFescape

PDFescape is a feature-rich online PDF annotator. You can use it right away without needing to create an account fist. Simply open the website of PDFescape and upload a PDF document you want to annotate and you can start working. PDFescape features nearly everything you need from an PDF annotator. You can add such elements as highlight, text, whiteout and so on. PDFescape itself is a freemium tool. Free version requires you to work with ads-displaying window. If you need to annotate some PDF documents frequent enough, you might can consider the paid version. In addition to ad-free, there are also some additional features you can get.

2. PDFfiller

The service offered by PDFfiller is quite similar to PDFescape. It offers a tool which you can use to annotate your PDF documents. You can also use PDFfiller for free, but premium version is also available in case you need more features. Unlike PDFescape, the free version of PDFfiller doesn’t require you to see ads. PDFfiller is also a feature-rich PDF annotator. It’s particularly a great tool if you need to add an e-signature to your PDF document. However, account is required before stepping further with the PDF document you have annotated. PDFfiller is integrated with such cloud storages as Dropbox, Box and OneDrive. Furthermore, PDFfiller also comes with a collaboration capability.

3. XODO PDF Reader

XODO PDF Reader is a free tool you can use to annotate your PDF documents. You can also use this tool right away without needing to create any account. Despite free, XODO PDF Reader has a bunch of features. You can use it to add e-signature to your document, highlighting certain sentences or adding missed text. XODO PDF Reader is also integrated with popular cloud storage services like Dropbox and Google Drive. If you have some PDF documents on Google Drive or Dropbox and need to annotate them, you can import them to XODO PDF Reader.

4. Annotate.co

Annotate.co is an online annotator that is aimed at team work. It also offers a free version in case you just need to annotate your PDF documents once. The free version of Annotate.co allows you to invite 3 members. It also integrated with Google Drive and Dropbox that makes it possible if you want to annotate existing PDF documents on both cloud storage services. The features offered by this tool are not much different to all tools above whereby you can add e-signature, highlight certain sentences and so on. You need to create an account before being able to use this tool.

5. DocHub

DocHub is a freemium online PDF annotator. It also comes with a collaboration capability. There are a bunch of tools you can find on the top menu of this tool which you can use to do such things as adding e-signature, highlighting sentences, adding text and many other more. This tool is also integrated with popular cloud storage services like Dropbox, Google Drive to OneDrive. DocHub features a handy file manager in case you want to store your documents on it. You are also required to create an account before being able to use this tool. Or, you can use either your Google account or Dropbox account.