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:
<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.