Using the AcroPDF.dll within the Microsoft WebBrowser control is unsupported
The Microsoft WebBrowser control is a . Net component that allows developers to create forms which can browse web pages. A side effect of this control is that it can also be used to display PDF files in the form through use of the AcroPDF.dll.
Adobe doesn't recommend or support use of the AcroPDF.dll in this way and developers who do implement this kind of solution to view PDF files within their application may encounter unexpected behavior.
Direct embedding of the AcroPDF control directly into the form itself is supported and this is documented in the Acrobat SDK. See the chapter entitled "Acrobat Interapplication Communication" and specifically the description of the AxAcroPDF object in the Interapplication Communication API Reference. This mechanism is supported in both Acrobat and Reader.
Acrobat allows other ways to make PDFs available within your own application and these are also described in the Acrobat SDK. These are documented here.