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PDFTron SDK for .NET Framework is a true .NET component and can be used by any .NET language (e.g. C#, VB.NET, etc). The assembly doesn't use PInvoke or COM interop and does not require/depend on other unmanaged non-system components. At the same,
PDFNet for .NET Framework, is a "mixed" component and is not "verifiable" since it has some native dependencies (e.g. for printer driver support, XPS printing, GDI, efficient image libs, COM interop etc - these features are by definition impossible to do in "verifiable" .NET components).
"AnyCPU" selection means different things in different versions of Visual Studio, however you can definitely make an "AnyCPU" configuration and make the app work correctly on both x86, x64, and other platforms. The issue is not PDFNet specific any there are many solutions:
The simplest option is to select 'x86' in your project solution. With this option the app will work on both x86 and x64 system.
A bit more complicated option is that you select 'Any CPU' mode in your app. As part of the app install you would copy/install a version of PDFNet that matches the target hardware (i.e. x86, x64). This is possible because both versions have the same signature/cert.
Alternatively you can register both the 32-bit as well as 64-bit DLLs in GAC.
In case you do not want to haver any app 'installer' and you still want to use 'Any CPU' there are also multiple options some which are outlined here http://stackoverflow.com/questions/108971/using-side-by-side-assemblies-to-load-the-x64-or-x32-version-of-a-dll.
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