pdfFileName, from disk,
and constructs a PDF handle as
*pdfPtr. This function
must be called before any of the functions that access a PDF file.
pdfLoadFileW is identical to
pdfLoadFile, except that
the file name is Unicode (
pdfLoadFile function returns
successful, otherwise an error code.
This function is only available on Windows.
IMPORTANT: The PDF file on disk must not be deleted or modified
pdfFree is called.