I am looking for a truly free (open source) PDF libary for c# with would enable me to annoate a PDF with a stylus.

  • Are you looking for an application or a library? If you're looking for a library, do you want it to just be able to annotate the PDF, or also to provide UI elements for displaying the PDF, which accepts the stylus input? If you also want the UI element, what UI platform (WPF, Winforms, UWP, Xamarin, …) are you using? – svick Mar 14 '17 at 18:30
  • @svick UI yes, Winforms – henry Mar 14 '17 at 19:14

You can use iTextSharp which is available in an open-source version, in combination with the System.Windows.Input.Stylus or System.Windows.Ink class. It is widely supported and has many APIs for inking and PDF creation.


Syncfusion Essential PDF Viewer for WPF is an option to consider. Here is a sample application.

Syncfusion PDF Annotations

The entire product is available for free through the community license program if you qualify (less than 1 million USD in revenue).

Note: I work for Syncfusion.

  • Thanks a lot ! This looks great ! Do you know, if it is also possible to implement Will Universal Ink from Wacom ? – henry Mar 17 '17 at 6:53
  • @DoHe We have analyzed Wacom’s WILL Universal Ink and they have provided SDKs for native iOS, native Android and WinRT. What platform do you need this for? – Davis Jebaraj Mar 30 '17 at 4:08
  • thanks a lot ! I need it for windows 10. – henry Mar 31 '17 at 4:50
  • @DoHe Wacom developer site only has SDKs for WinRT. For Windows 10, we would need a .NET or UWP SDK. Do you know if they provide those? – Davis Jebaraj Apr 11 '17 at 21:04
  • No, I am afraid, I don't know – henry Apr 12 '17 at 11:32

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