Despite the error message, the issue isn't 64-bit vs 32-bit.
The problem is that Screenwriter, like almost every other application, doesn't import PDF documents.
If you want to import from Microsoft Word, then you need to use Microsoft's RTF (Rich Text Format). You can also open your document in Word, select all text, copy and paste into Screenwriter. This can be effective, but depends on how consistent your Word document follows screenplay conventions.
Here is a link with directions for getting the contents of a PDF file into Movie Magic Screenwriter: