Q.  I'm using Toolkit 10.1.0 and pointed my reference to the
C:\Program Files\activePDF\Toolkit\bin\x64\APToolkitNET.dll

I am making sure my console project is a .net framework 4.7 and the following code throws "System.ArgumentException: 'Core library not loaded Parameter name: Toolkit'"

using (APToolkitNET.Toolkit tk = new APToolkitNET.Toolkit()) 

Any ideas? This looks like something is .NET Core but I'm not using .NET Core

A. There are some changes in the Toolkit installation beginning with 10.1.0
Please see Toolkit Release Notes 10.1.0

Starting with TK 10.1.0, the core Toolkit files are no longer installed in the c:\Windows\System32 or c:\Windows\SysWOW64 folders. The files are now installed in the folder C:\Program Files\ActivePDF\Toolkit\bin. You must update your .NET application to explicitly reference the location of the Toolkit files. 

The following example is a code snippet to reference the Toolkit files located 
C:\Program Files\ActivePDF\Toolkit\bin\x64: 

APToolkitNET.Toolkit oTK = new APToolkitNET.Toolkit(@"C:\Program Files\ActivePDF\Toolkit\bin\x64");


== Notes for 64-bit project & NuGet download ==

Additionally, if you reference the 64-bit DLLs in C:\Program Files\ActivePDF\Toolkit\bin\x64, or download the Toolkit NuGet package (which is 64-bit), then:

Go to your Visual Studio solution, and then to 

Project> Properties> Build > Platform Target and uncheck the Prefer 32-bit box. Leave the platform set to Any CPU.
See attached image.

== Update == Web Apps

Issue: Console app works with the information above, but Web App still fails.

After further investigation, we found the reason why it worked on a certain machine is because TK 9.1.0 or below existed with the DLLs in system32 or System64 folders.. If installing Toolkit 10.1.0 on a fresh, clean machine that never previously had Toolkit installed will fail on Web App.

For some reason TK 10.1 and TKU for Web Apps, looks in the system32 or System64 folders for the DLLs. The installers do not not copy the DLLs in those folder.


  • C:\Program Files\ActivePDF\Toolkit Ultimate\bin\x64 or x86

  • Copy the DLLs to the System32 or SysWOW64 bit folder

x86-For 32 bit DLL: Copy the DLLs to the SysWOW64

x64-For 64 bit DLL:  Copy the DLLs to the System32