ActivePDF Toolkit can be used with Microsoft's Azure App Services, it does require an extra step to function. The Toolkit .NET wrapper requires the native DLLs installed with Toolkit to work. For an Azure App Service using Toolkit that means the native DLLs need to be uploaded to the App service container. This is a straightforward part off publishing your app service but for Toolkit the directory with the native DLLs must be added to the PATH environment variable. The simplest way to edit the PATH environment variable is to apply a XDT file to your applicaitonhost.config.

Create a file named applicationHost.xdt, or open the current one for editing, and add the following:

<?xml version="1.0"?> 
<configuration xmlns:xdt="">
<runtime xdt:Transform="InsertIfMissing">
<environmentVariables xdt:Transform="InsertIfMissing">
<add name="PATH" value="%PATH%;[FolderOnPath]" xdt:Locator="Match(name)" xdt:Transform="InsertIfMissing" />

* Replace [FolderOnPath] with the directory you wish to add to PATH.

Place the newly generated, or edited, XDT file in your site root and restart your service. The added directory can take some time to appear on the environment PATH. Once the path to your Toolkit DLLs appears on the environment PATH your App Service should be able to load the native DLLs.

See sample code ToolkitCopyFormWebApp - Note: Be sure to change the App Service Platform settings to the corresponding 64bit vs. 32bit App (see image).  By default it is set to 32-bit, however, if you are using Toolkit 64-bit, then you'll need to make the change.

A note about licensing:

You will need a different type of license for Azure Web Apps. The standard license model for production/developer  licenses are per machine and not valid to be used in a cloud application. These licenses are not embedded in the DLL but installed to your machine through the ActivePDF License Administrator. Toolkit has a royalty free license option for use in a cloud environment, it allows you to use a file in your application with the license or a runtime key in your code.